Annual report pursuant to Section 13 and 15(d)

Schedule III - Real Estate and Accumulated Depreciation (Details)

v2.4.1.9
Schedule III - Real Estate and Accumulated Depreciation (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Real Estate and Accumulated Depreciation        
Encumbrances $ 409,193,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances [1]      
Initial Cost        
Land 668,660,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand      
Building and Land Improvements 3,008,508,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements      
Costs Capitalized Subsequent to Acquisition 337,168,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts      
Gross Amounts Carried at Close of Period        
Land 668,660,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand      
Building and Land Improvements 3,345,676,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements      
Total 4,014,336,000us-gaap_RealEstateGrossAtCarryingValue [2],[3] 3,811,950,000us-gaap_RealEstateGrossAtCarryingValue 3,859,960,000us-gaap_RealEstateGrossAtCarryingValue 4,038,932,000us-gaap_RealEstateGrossAtCarryingValue
Accumulated Depreciation (703,083,000)us-gaap_RealEstateAccumulatedDepreciation [4] (597,649,000)us-gaap_RealEstateAccumulatedDepreciation (568,176,000)us-gaap_RealEstateAccumulatedDepreciation (577,601,000)us-gaap_RealEstateAccumulatedDepreciation
Additional information        
Debt excluded from encumbrances 1,920,057,000us-gaap_LongTermDebt 1,927,703,000us-gaap_LongTermDebt    
Aggregate cost of assets for federal income tax purposes 3,400,000,000us-gaap_RealEstateFederalIncomeTaxBasis      
Impairment losses 1,416,000us-gaap_AssetImpairmentCharges 5,857,000us-gaap_AssetImpairmentCharges 43,678,000us-gaap_AssetImpairmentCharges  
Buildings improvements | Minimum        
Additional information        
Estimated lives over which depreciation is recognized 10 years      
Buildings improvements | Maximum        
Additional information        
Estimated lives over which depreciation is recognized 40 years      
Revolving Credit Facility        
Additional information        
Debt excluded from encumbrances 83,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember
0us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember
   
Term Loan Facilities        
Additional information        
Debt excluded from encumbrances 520,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember
620,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember
   
Senior Unsecured Notes        
Additional information        
Debt excluded from encumbrances 890,900,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_SeniorNotesMember
     
4.25% Exchangeable Senior Notes        
Additional information        
Debt excluded from encumbrances 572,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember
563,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember
   
Unsecured notes payable        
Additional information        
Debt excluded from encumbrances 1,607,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember
1,700,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember
   
Letter of Credit        
Additional information        
Debt excluded from encumbrances 14,800,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_LetterOfCreditMember
     
Fixed rate mortgage loans        
Additional information        
Debt excluded from encumbrances 387,139,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember
675,060,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember
   
Unamortized premium included in carrying value 42,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember
69,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember
   
1000 Redstone Gateway        
Real Estate and Accumulated Depreciation        
Encumbrances 11,671,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1000RedstoneGatewayMember
[1]      
Initial Cost        
Building and Land Improvements 20,527,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1000RedstoneGatewayMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 20,527,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1000RedstoneGatewayMember
     
Total 20,527,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1000RedstoneGatewayMember
[2],[3]      
Accumulated Depreciation (924,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1000RedstoneGatewayMember
[4]      
1100 Redstone Gateway        
Real Estate and Accumulated Depreciation        
Encumbrances 12,057,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1100RedstoneGatewayMember
[1]      
Initial Cost        
Building and Land Improvements 19,501,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1100RedstoneGatewayMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 19,501,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1100RedstoneGatewayMember
     
Total 19,501,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1100RedstoneGatewayMember
[2],[3]      
Accumulated Depreciation (476,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1100RedstoneGatewayMember
[4]      
114 National Business Parkway        
Initial Cost        
Land 364,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number114NationalBusinessParkwayMember
     
Building and Land Improvements 3,109,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number114NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 46,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number114NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 364,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number114NationalBusinessParkwayMember
     
Building and Land Improvements 3,155,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number114NationalBusinessParkwayMember
     
Total 3,519,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number114NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (1,042,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number114NationalBusinessParkwayMember
[4]      
11751 Meadowville Lane        
Initial Cost        
Land 1,305,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number11751MeadowvilleLaneMember
     
Building and Land Improvements 52,098,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number11751MeadowvilleLaneMember
     
Costs Capitalized Subsequent to Acquisition 112,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number11751MeadowvilleLaneMember
     
Gross Amounts Carried at Close of Period        
Land 1,305,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number11751MeadowvilleLaneMember
     
Building and Land Improvements 52,210,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number11751MeadowvilleLaneMember
     
Total 53,515,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number11751MeadowvilleLaneMember
[2],[3]      
Accumulated Depreciation (9,889,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number11751MeadowvilleLaneMember
[4]      
1200 Redstone Gateway        
Real Estate and Accumulated Depreciation        
Encumbrances 13,950,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1200RedstoneGatewayMember
[1]      
Initial Cost        
Building and Land Improvements 22,409,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1200RedstoneGatewayMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 22,409,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1200RedstoneGatewayMember
     
Total 22,409,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1200RedstoneGatewayMember
[2],[3]      
Accumulated Depreciation (586,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1200RedstoneGatewayMember
[4]      
1201 M Street        
Initial Cost        
Building and Land Improvements 49,785,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201MStreetMember
     
Costs Capitalized Subsequent to Acquisition 2,455,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201MStreetMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 52,240,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201MStreetMember
     
Total 52,240,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201MStreetMember
[2],[3]      
Accumulated Depreciation (7,255,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201MStreetMember
[4]      
1201 Winterson Road        
Initial Cost        
Land 1,288,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201WintersonRoadMember
[5]      
Building and Land Improvements 5,452,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201WintersonRoadMember
[5]      
Costs Capitalized Subsequent to Acquisition 460,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201WintersonRoadMember
[5]      
Gross Amounts Carried at Close of Period        
Land 1,288,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201WintersonRoadMember
[5]      
Building and Land Improvements 5,912,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201WintersonRoadMember
[5]      
Total 7,200,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201WintersonRoadMember
[2],[3],[5]      
Accumulated Depreciation (2,388,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1201WintersonRoadMember
[4],[5]      
1220 12th Street, SE        
Initial Cost        
Building and Land Improvements 42,464,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number122012ThStreetSeMember
     
Costs Capitalized Subsequent to Acquisition 2,014,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number122012ThStreetSeMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 44,478,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number122012ThStreetSeMember
     
Total 44,478,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number122012ThStreetSeMember
[2],[3]      
Accumulated Depreciation (7,143,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number122012ThStreetSeMember
[4]      
1243 Winterson Road        
Initial Cost        
Land 630,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1243WintersonRoadMember
[6]      
Gross Amounts Carried at Close of Period        
Land 630,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1243WintersonRoadMember
[6]      
Total 630,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1243WintersonRoadMember
[2],[3],[6]      
1302 Concourse Drive        
Initial Cost        
Land 2,078,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1302ConcourseDriveMember
     
Building and Land Improvements 8,313,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1302ConcourseDriveMember
     
Costs Capitalized Subsequent to Acquisition 5,008,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1302ConcourseDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,078,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1302ConcourseDriveMember
     
Building and Land Improvements 13,321,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1302ConcourseDriveMember
     
Total 15,399,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1302ConcourseDriveMember
[2],[3]      
Accumulated Depreciation (5,610,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1302ConcourseDriveMember
[4]      
1304 Concourse Drive        
Initial Cost        
Land 1,999,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1304ConcourseDriveMember
     
Building and Land Improvements 12,934,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1304ConcourseDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,594,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1304ConcourseDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,999,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1304ConcourseDriveMember
     
Building and Land Improvements 15,528,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1304ConcourseDriveMember
     
Total 17,527,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1304ConcourseDriveMember
[2],[3]      
Accumulated Depreciation (5,680,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1304ConcourseDriveMember
[4]      
1306 Concourse Drive        
Initial Cost        
Land 2,796,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1306ConcourseDriveMember
     
Building and Land Improvements 11,186,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1306ConcourseDriveMember
     
Costs Capitalized Subsequent to Acquisition 5,745,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1306ConcourseDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,796,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1306ConcourseDriveMember
     
Building and Land Improvements 16,931,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1306ConcourseDriveMember
     
Total 19,727,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1306ConcourseDriveMember
[2],[3]      
Accumulated Depreciation (6,097,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1306ConcourseDriveMember
[4]      
131 National Business Parkway        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number131NationalBusinessParkwayMember
[1]      
Initial Cost        
Land 1,906,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number131NationalBusinessParkwayMember
     
Building and Land Improvements 7,623,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number131NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 3,288,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number131NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 1,906,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number131NationalBusinessParkwayMember
     
Building and Land Improvements 10,911,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number131NationalBusinessParkwayMember
     
Total 12,817,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number131NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (4,807,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number131NationalBusinessParkwayMember
[4]      
132 National Business Parkway        
Initial Cost        
Land 2,917,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number132NationalBusinessParkwayMember
     
Building and Land Improvements 12,259,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number132NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 2,977,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number132NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 2,917,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number132NationalBusinessParkwayMember
     
Building and Land Improvements 15,236,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number132NationalBusinessParkwayMember
     
Total 18,153,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number132NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (7,314,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number132NationalBusinessParkwayMember
[4]      
13200 Woodland Park Road        
Initial Cost        
Land 10,428,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13200WoodlandParkRoadMember
     
Building and Land Improvements 41,711,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13200WoodlandParkRoadMember
     
Costs Capitalized Subsequent to Acquisition 13,985,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13200WoodlandParkRoadMember
     
Gross Amounts Carried at Close of Period        
Land 10,428,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13200WoodlandParkRoadMember
     
Building and Land Improvements 55,696,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13200WoodlandParkRoadMember
     
Total 66,124,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13200WoodlandParkRoadMember
[2],[3]      
Accumulated Depreciation (24,106,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13200WoodlandParkRoadMember
[4]      
133 National Business Parkway        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number133NationalBusinessParkwayMember
[1]      
Initial Cost        
Land 2,517,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number133NationalBusinessParkwayMember
     
Building and Land Improvements 10,068,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number133NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 4,920,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number133NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 2,517,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number133NationalBusinessParkwayMember
     
Building and Land Improvements 14,988,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number133NationalBusinessParkwayMember
     
Total 17,505,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number133NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (7,560,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number133NationalBusinessParkwayMember
[4]      
1331 Ashton Road        
Initial Cost        
Land 587,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1331AshtonRoadMember
     
Building and Land Improvements 2,347,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1331AshtonRoadMember
     
Costs Capitalized Subsequent to Acquisition 1,474,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1331AshtonRoadMember
     
Gross Amounts Carried at Close of Period        
Land 587,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1331AshtonRoadMember
     
Building and Land Improvements 3,821,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1331AshtonRoadMember
     
Total 4,408,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1331AshtonRoadMember
[2],[3]      
Accumulated Depreciation (1,154,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1331AshtonRoadMember
[4]      
1334 Ashton Road        
Initial Cost        
Land 736,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1334AshtonRoadMember
     
Building and Land Improvements 1,488,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1334AshtonRoadMember
     
Costs Capitalized Subsequent to Acquisition 2,634,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1334AshtonRoadMember
     
Gross Amounts Carried at Close of Period        
Land 736,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1334AshtonRoadMember
     
Building and Land Improvements 4,122,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1334AshtonRoadMember
     
Total 4,858,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1334AshtonRoadMember
[2],[3]      
Accumulated Depreciation (2,055,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1334AshtonRoadMember
[4]      
134 National Business Parkway        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number134NationalBusinessParkwayMember
[1]      
Initial Cost        
Land 3,684,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number134NationalBusinessParkwayMember
     
Building and Land Improvements 7,517,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number134NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 1,282,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number134NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 3,684,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number134NationalBusinessParkwayMember
     
Building and Land Improvements 8,799,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number134NationalBusinessParkwayMember
     
Total 12,483,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number134NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (3,765,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number134NationalBusinessParkwayMember
[4]      
1340 Ashton Road        
Initial Cost        
Land 905,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1340AshtonRoadMember
     
Building and Land Improvements 3,620,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1340AshtonRoadMember
     
Costs Capitalized Subsequent to Acquisition 1,466,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1340AshtonRoadMember
     
Gross Amounts Carried at Close of Period        
Land 905,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1340AshtonRoadMember
     
Building and Land Improvements 5,086,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1340AshtonRoadMember
     
Total 5,991,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1340AshtonRoadMember
[2],[3]      
Accumulated Depreciation (2,431,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1340AshtonRoadMember
[4]      
1341 Ashton Road        
Initial Cost        
Land 306,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1341AshtonRoadMember
     
Building and Land Improvements 1,223,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1341AshtonRoadMember
     
Costs Capitalized Subsequent to Acquisition 601,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1341AshtonRoadMember
     
Gross Amounts Carried at Close of Period        
Land 306,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1341AshtonRoadMember
     
Building and Land Improvements 1,824,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1341AshtonRoadMember
     
Total 2,130,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1341AshtonRoadMember
[2],[3]      
Accumulated Depreciation (860,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1341AshtonRoadMember
[4]      
1343 Ashton Road        
Initial Cost        
Land 193,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1343AshtonRoadMember
     
Building and Land Improvements 774,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1343AshtonRoadMember
     
Costs Capitalized Subsequent to Acquisition 405,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1343AshtonRoadMember
     
Gross Amounts Carried at Close of Period        
Land 193,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1343AshtonRoadMember
     
Building and Land Improvements 1,179,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1343AshtonRoadMember
     
Total 1,372,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1343AshtonRoadMember
[2],[3]      
Accumulated Depreciation (596,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1343AshtonRoadMember
[4]      
13450 Sunrise Valley Road        
Initial Cost        
Land 1,386,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13450SunriseValleyRoadMember
     
Building and Land Improvements 5,576,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13450SunriseValleyRoadMember
     
Costs Capitalized Subsequent to Acquisition 3,335,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13450SunriseValleyRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,386,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13450SunriseValleyRoadMember
     
Building and Land Improvements 8,911,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13450SunriseValleyRoadMember
     
Total 10,297,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13450SunriseValleyRoadMember
[2],[3]      
Accumulated Depreciation (3,580,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13450SunriseValleyRoadMember
[4]      
13454 Sunrise Valley Road        
Initial Cost        
Land 2,899,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13454SunriseValleyRoadMember
     
Building and Land Improvements 11,986,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13454SunriseValleyRoadMember
     
Costs Capitalized Subsequent to Acquisition 5,447,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13454SunriseValleyRoadMember
     
Gross Amounts Carried at Close of Period        
Land 2,899,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13454SunriseValleyRoadMember
     
Building and Land Improvements 17,433,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13454SunriseValleyRoadMember
     
Total 20,332,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13454SunriseValleyRoadMember
[2],[3]      
Accumulated Depreciation (6,255,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13454SunriseValleyRoadMember
[4]      
135 National Business Parkway        
Real Estate and Accumulated Depreciation        
Encumbrances 11,418,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number135NationalBusinessParkwayMember
[1]      
Initial Cost        
Land 2,484,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number135NationalBusinessParkwayMember
     
Building and Land Improvements 9,750,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number135NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 4,742,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number135NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 2,484,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number135NationalBusinessParkwayMember
     
Building and Land Improvements 14,492,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number135NationalBusinessParkwayMember
     
Total 16,976,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number135NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (5,845,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number135NationalBusinessParkwayMember
[4]      
1362 Mellon Road        
Initial Cost        
Land 1,706,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1362MellonRoadMember
     
Building and Land Improvements 8,670,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1362MellonRoadMember
     
Costs Capitalized Subsequent to Acquisition 119,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1362MellonRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,706,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1362MellonRoadMember
     
Building and Land Improvements 8,789,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1362MellonRoadMember
     
Total 10,495,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1362MellonRoadMember
[2],[3]      
Accumulated Depreciation (1,278,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1362MellonRoadMember
[4]      
13857 McLearen Road        
Initial Cost        
Land 3,507,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13857MclearenRoadMember
     
Building and Land Improvements 30,177,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13857MclearenRoadMember
     
Costs Capitalized Subsequent to Acquisition 1,557,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13857MclearenRoadMember
     
Gross Amounts Carried at Close of Period        
Land 3,507,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13857MclearenRoadMember
     
Building and Land Improvements 31,734,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13857MclearenRoadMember
     
Total 35,241,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13857MclearenRoadMember
[2],[3]      
Accumulated Depreciation (4,945,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number13857MclearenRoadMember
[4]      
140 National Business Parkway        
Initial Cost        
Land 3,407,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number140NationalBusinessParkwayMember
     
Building and Land Improvements 24,167,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number140NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 643,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number140NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 3,407,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number140NationalBusinessParkwayMember
     
Building and Land Improvements 24,810,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number140NationalBusinessParkwayMember
     
Total 28,217,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number140NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (7,039,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number140NationalBusinessParkwayMember
[4]      
141 National Business Parkway        
Real Estate and Accumulated Depreciation        
Encumbrances 11,871,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number141NationalBusinessParkwayMember
[1]      
Initial Cost        
Land 2,398,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number141NationalBusinessParkwayMember
     
Building and Land Improvements 9,590,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number141NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 2,995,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number141NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 2,398,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number141NationalBusinessParkwayMember
     
Building and Land Improvements 12,585,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number141NationalBusinessParkwayMember
     
Total 14,983,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number141NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (5,575,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number141NationalBusinessParkwayMember
[4]      
14280 Park Meadow Drive        
Initial Cost        
Land 3,731,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14280ParkMeadowDriveMember
     
Building and Land Improvements 15,953,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14280ParkMeadowDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,754,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14280ParkMeadowDriveMember
     
Gross Amounts Carried at Close of Period        
Land 3,731,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14280ParkMeadowDriveMember
     
Building and Land Improvements 17,707,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14280ParkMeadowDriveMember
     
Total 21,438,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14280ParkMeadowDriveMember
[2],[3]      
Accumulated Depreciation (5,626,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14280ParkMeadowDriveMember
[4]      
1460 Dorsey Road        
Initial Cost        
Land 1,800,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1460DorseyRoadMember
[6]      
Gross Amounts Carried at Close of Period        
Land 1,800,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1460DorseyRoadMember
[6]      
Total 1,800,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1460DorseyRoadMember
[2],[3],[6]      
14840 Conference Center Drive        
Initial Cost        
Land 1,572,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14840ConferenceCenterDriveMember
     
Building and Land Improvements 8,175,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14840ConferenceCenterDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,488,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14840ConferenceCenterDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,572,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14840ConferenceCenterDriveMember
     
Building and Land Improvements 9,663,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14840ConferenceCenterDriveMember
     
Total 11,235,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14840ConferenceCenterDriveMember
[2],[3]      
Accumulated Depreciation (3,885,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14840ConferenceCenterDriveMember
[4]      
14850 Conference Center Drive        
Initial Cost        
Land 1,615,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14850ConferenceCenterDriveMember
     
Building and Land Improvements 8,358,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14850ConferenceCenterDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,896,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14850ConferenceCenterDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,615,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14850ConferenceCenterDriveMember
     
Building and Land Improvements 11,254,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14850ConferenceCenterDriveMember
     
Total 12,869,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14850ConferenceCenterDriveMember
[2],[3]      
Accumulated Depreciation (4,074,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14850ConferenceCenterDriveMember
[4]      
14900 Conference Center Drive        
Initial Cost        
Land 3,436,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14900ConferenceCenterDriveMember
     
Building and Land Improvements 14,402,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14900ConferenceCenterDriveMember
     
Costs Capitalized Subsequent to Acquisition 4,569,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14900ConferenceCenterDriveMember
     
Gross Amounts Carried at Close of Period        
Land 3,436,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14900ConferenceCenterDriveMember
     
Building and Land Improvements 18,971,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14900ConferenceCenterDriveMember
     
Total 22,407,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14900ConferenceCenterDriveMember
[2],[3]      
Accumulated Depreciation (7,396,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number14900ConferenceCenterDriveMember
[4]      
15000 Conference Center Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 54,000,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15000ConferenceCenterDriveMember
[1]      
Initial Cost        
Land 5,193,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15000ConferenceCenterDriveMember
     
Building and Land Improvements 47,045,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15000ConferenceCenterDriveMember
     
Costs Capitalized Subsequent to Acquisition 18,692,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15000ConferenceCenterDriveMember
     
Gross Amounts Carried at Close of Period        
Land 5,193,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15000ConferenceCenterDriveMember
     
Building and Land Improvements 65,737,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15000ConferenceCenterDriveMember
     
Total 70,930,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15000ConferenceCenterDriveMember
[2],[3]      
Accumulated Depreciation (25,365,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15000ConferenceCenterDriveMember
[4]      
1501 South Clinton Street        
Initial Cost        
Land 27,964,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1501SouthClintonStreetMember
     
Building and Land Improvements 52,146,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1501SouthClintonStreetMember
     
Costs Capitalized Subsequent to Acquisition 7,553,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1501SouthClintonStreetMember
     
Gross Amounts Carried at Close of Period        
Land 27,964,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1501SouthClintonStreetMember
     
Building and Land Improvements 59,699,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1501SouthClintonStreetMember
     
Total 87,663,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1501SouthClintonStreetMember
[2],[3]      
Accumulated Depreciation (11,059,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1501SouthClintonStreetMember
[4]      
15010 Conference Center Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 96,000,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15010ConferenceCenterDriveMember
[1]      
Initial Cost        
Land 3,500,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15010ConferenceCenterDriveMember
     
Building and Land Improvements 41,921,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15010ConferenceCenterDriveMember
     
Costs Capitalized Subsequent to Acquisition 498,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15010ConferenceCenterDriveMember
     
Gross Amounts Carried at Close of Period        
Land 3,500,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15010ConferenceCenterDriveMember
     
Building and Land Improvements 42,419,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15010ConferenceCenterDriveMember
     
Total 45,919,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15010ConferenceCenterDriveMember
[2],[3]      
Accumulated Depreciation (8,644,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15010ConferenceCenterDriveMember
[4]      
15049 Conference Center Drive        
Initial Cost        
Land 4,415,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15049ConferenceCenterDriveMember
     
Building and Land Improvements 20,365,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15049ConferenceCenterDriveMember
     
Costs Capitalized Subsequent to Acquisition 726,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15049ConferenceCenterDriveMember
     
Gross Amounts Carried at Close of Period        
Land 4,415,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15049ConferenceCenterDriveMember
     
Building and Land Improvements 21,091,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15049ConferenceCenterDriveMember
     
Total 25,506,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15049ConferenceCenterDriveMember
[2],[3]      
Accumulated Depreciation (8,781,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15049ConferenceCenterDriveMember
[4]      
15059 Conference Center Drive        
Initial Cost        
Land 5,753,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15059ConferenceCenterDriveMember
     
Building and Land Improvements 13,615,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15059ConferenceCenterDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,780,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15059ConferenceCenterDriveMember
     
Gross Amounts Carried at Close of Period        
Land 5,753,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15059ConferenceCenterDriveMember
     
Building and Land Improvements 15,395,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15059ConferenceCenterDriveMember
     
Total 21,148,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15059ConferenceCenterDriveMember
[2],[3]      
Accumulated Depreciation (6,071,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15059ConferenceCenterDriveMember
[4]      
15395 John Marshall Highway        
Initial Cost        
Land 2,465,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15395JohnMarshallHighwayMember
     
Building and Land Improvements 24,720,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15395JohnMarshallHighwayMember
     
Gross Amounts Carried at Close of Period        
Land 2,465,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15395JohnMarshallHighwayMember
     
Building and Land Improvements 24,720,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15395JohnMarshallHighwayMember
     
Total 27,185,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15395JohnMarshallHighwayMember
[2],[3]      
Accumulated Depreciation (576,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number15395JohnMarshallHighwayMember
[4]      
1550 West Nursery Road        
Initial Cost        
Land 14,071,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestNurseryRoadMember
     
Building and Land Improvements 16,930,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestNurseryRoadMember
     
Gross Amounts Carried at Close of Period        
Land 14,071,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestNurseryRoadMember
     
Building and Land Improvements 16,930,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestNurseryRoadMember
     
Total 31,001,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestNurseryRoadMember
[2],[3]      
Accumulated Depreciation (3,038,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestNurseryRoadMember
[4]      
1550 Westbranch Drive        
Initial Cost        
Land 5,595,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestbranchDriveMember
     
Building and Land Improvements 26,212,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestbranchDriveMember
     
Costs Capitalized Subsequent to Acquisition 116,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestbranchDriveMember
     
Gross Amounts Carried at Close of Period        
Land 5,595,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestbranchDriveMember
     
Building and Land Improvements 26,328,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestbranchDriveMember
     
Total 31,923,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestbranchDriveMember
[2],[3]      
Accumulated Depreciation (3,647,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1550WestbranchDriveMember
[4]      
1560 West Nursery Road        
Initial Cost        
Land 1,441,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560WestNurseryRoadMember
     
Building and Land Improvements 96,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560WestNurseryRoadMember
     
Costs Capitalized Subsequent to Acquisition 0us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560WestNurseryRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,441,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560WestNurseryRoadMember
     
Building and Land Improvements 96,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560WestNurseryRoadMember
     
Total 1,537,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560WestNurseryRoadMember
[2],[3]      
Accumulated Depreciation (2,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560WestNurseryRoadMember
[4]      
1560A Cable Ranch Road        
Initial Cost        
Land 1,097,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560CableRanchRoadMember
     
Building and Land Improvements 3,770,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560CableRanchRoadMember
     
Costs Capitalized Subsequent to Acquisition 352,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560CableRanchRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,097,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560CableRanchRoadMember
     
Building and Land Improvements 4,122,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560CableRanchRoadMember
     
Total 5,219,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560CableRanchRoadMember
[2],[3]      
Accumulated Depreciation (950,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560CableRanchRoadMember
[4]      
1560B Cable Ranch Road        
Initial Cost        
Land 2,299,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560BCableRanchRoadMember
     
Building and Land Improvements 6,545,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560BCableRanchRoadMember
     
Costs Capitalized Subsequent to Acquisition 11,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560BCableRanchRoadMember
     
Gross Amounts Carried at Close of Period        
Land 2,299,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560BCableRanchRoadMember
     
Building and Land Improvements 6,556,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560BCableRanchRoadMember
     
Total 8,855,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560BCableRanchRoadMember
[2],[3]      
Accumulated Depreciation (1,532,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1560BCableRanchRoadMember
[4]      
16442 Commerce Drive        
Initial Cost        
Land 613,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16442CommerceDriveMember
     
Building and Land Improvements 2,582,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16442CommerceDriveMember
     
Costs Capitalized Subsequent to Acquisition 593,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16442CommerceDriveMember
     
Gross Amounts Carried at Close of Period        
Land 613,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16442CommerceDriveMember
     
Building and Land Improvements 3,175,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16442CommerceDriveMember
     
Total 3,788,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16442CommerceDriveMember
[2],[3]      
Accumulated Depreciation (1,153,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16442CommerceDriveMember
[4]      
16480 Commerce Drive        
Initial Cost        
Land 1,856,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16480CommerceDriveMember
     
Building and Land Improvements 7,425,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16480CommerceDriveMember
     
Costs Capitalized Subsequent to Acquisition 167,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16480CommerceDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,856,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16480CommerceDriveMember
     
Building and Land Improvements 7,592,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16480CommerceDriveMember
     
Total 9,448,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16480CommerceDriveMember
[2],[3]      
Accumulated Depreciation (2,020,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16480CommerceDriveMember
[4]      
16501 Commerce Drive        
Initial Cost        
Land 522,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16501CommerceDriveMember
     
Building and Land Improvements 2,090,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16501CommerceDriveMember
     
Costs Capitalized Subsequent to Acquisition 465,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16501CommerceDriveMember
     
Gross Amounts Carried at Close of Period        
Land 522,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16501CommerceDriveMember
     
Building and Land Improvements 2,555,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16501CommerceDriveMember
     
Total 3,077,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16501CommerceDriveMember
[2],[3]      
Accumulated Depreciation (714,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16501CommerceDriveMember
[4]      
16539 Commerce Drive        
Initial Cost        
Land 688,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16539CommerceDriveMember
     
Building and Land Improvements 2,860,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16539CommerceDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,469,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16539CommerceDriveMember
     
Gross Amounts Carried at Close of Period        
Land 688,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16539CommerceDriveMember
     
Building and Land Improvements 4,329,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16539CommerceDriveMember
     
Total 5,017,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16539CommerceDriveMember
[2],[3]      
Accumulated Depreciation (1,696,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16539CommerceDriveMember
[4]      
16541 Commerce Drive        
Initial Cost        
Land 773,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16541CommerceDriveMember
     
Building and Land Improvements 3,094,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16541CommerceDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,367,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16541CommerceDriveMember
     
Gross Amounts Carried at Close of Period        
Land 773,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16541CommerceDriveMember
     
Building and Land Improvements 4,461,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16541CommerceDriveMember
     
Total 5,234,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16541CommerceDriveMember
[2],[3]      
Accumulated Depreciation (1,529,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16541CommerceDriveMember
[4]      
16543 Commerce Drive        
Initial Cost        
Land 436,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16543CommerceDriveMember
     
Building and Land Improvements 1,742,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16543CommerceDriveMember
     
Costs Capitalized Subsequent to Acquisition 172,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16543CommerceDriveMember
     
Gross Amounts Carried at Close of Period        
Land 436,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16543CommerceDriveMember
     
Building and Land Improvements 1,914,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16543CommerceDriveMember
     
Total 2,350,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16543CommerceDriveMember
[2],[3]      
Accumulated Depreciation (486,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number16543CommerceDriveMember
[4]      
1751 Pinnacle Drive        
Initial Cost        
Land 10,486,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1751PinnacleDriveMember
     
Building and Land Improvements 42,339,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1751PinnacleDriveMember
     
Costs Capitalized Subsequent to Acquisition 22,325,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1751PinnacleDriveMember
     
Gross Amounts Carried at Close of Period        
Land 10,486,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1751PinnacleDriveMember
     
Building and Land Improvements 64,664,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1751PinnacleDriveMember
     
Total 75,150,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1751PinnacleDriveMember
[2],[3]      
Accumulated Depreciation (20,705,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1751PinnacleDriveMember
[4]      
1753 Pinnacle Drive        
Initial Cost        
Land 8,275,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1753PinnacleDriveMember
     
Building and Land Improvements 34,353,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1753PinnacleDriveMember
     
Costs Capitalized Subsequent to Acquisition 10,528,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1753PinnacleDriveMember
     
Gross Amounts Carried at Close of Period        
Land 8,275,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1753PinnacleDriveMember
     
Building and Land Improvements 44,881,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1753PinnacleDriveMember
     
Total 53,156,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1753PinnacleDriveMember
[2],[3]      
Accumulated Depreciation (14,406,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number1753PinnacleDriveMember
[4]      
201 Technology Drive        
Initial Cost        
Land 726,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number201TechnologyDriveMember
     
Building and Land Improvements 31,091,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number201TechnologyDriveMember
     
Costs Capitalized Subsequent to Acquisition 60,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number201TechnologyDriveMember
     
Gross Amounts Carried at Close of Period        
Land 726,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number201TechnologyDriveMember
     
Building and Land Improvements 31,151,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number201TechnologyDriveMember
     
Total 31,877,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number201TechnologyDriveMember
[2],[3]      
Accumulated Depreciation (5,579,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number201TechnologyDriveMember
[4]      
206 Research Boulevard        
Initial Cost        
Land 1,813,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number206ResearchBoulevardMember
     
Building and Land Improvements 17,485,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number206ResearchBoulevardMember
     
Gross Amounts Carried at Close of Period        
Land 1,813,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number206ResearchBoulevardMember
     
Building and Land Improvements 17,485,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number206ResearchBoulevardMember
     
Total 19,298,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number206ResearchBoulevardMember
[2],[3]      
Accumulated Depreciation (979,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number206ResearchBoulevardMember
[4]      
209 Research Boulevard        
Initial Cost        
Land 1,045,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number209ResearchBoulevardMember
     
Building and Land Improvements 16,087,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number209ResearchBoulevardMember
     
Costs Capitalized Subsequent to Acquisition 32,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number209ResearchBoulevardMember
     
Gross Amounts Carried at Close of Period        
Land 1,045,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number209ResearchBoulevardMember
     
Building and Land Improvements 16,119,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number209ResearchBoulevardMember
     
Total 17,164,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number209ResearchBoulevardMember
[2],[3]      
Accumulated Depreciation (1,665,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number209ResearchBoulevardMember
[4]      
210 Research Boulevard        
Initial Cost        
Land 1,065,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number210ResearchBoulevardMember
     
Building and Land Improvements 14,687,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number210ResearchBoulevardMember
     
Costs Capitalized Subsequent to Acquisition 75,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number210ResearchBoulevardMember
     
Gross Amounts Carried at Close of Period        
Land 1,065,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number210ResearchBoulevardMember
     
Building and Land Improvements 14,762,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number210ResearchBoulevardMember
     
Total 15,827,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number210ResearchBoulevardMember
[2],[3]      
Accumulated Depreciation (1,191,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number210ResearchBoulevardMember
[4]      
21267 Smith Switch Road        
Initial Cost        
Land 4,040,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21267SmithSwitchRoadMember
     
Building and Land Improvements 10,369,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21267SmithSwitchRoadMember
     
Gross Amounts Carried at Close of Period        
Land 4,040,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21267SmithSwitchRoadMember
     
Building and Land Improvements 10,369,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21267SmithSwitchRoadMember
     
Total 14,409,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21267SmithSwitchRoadMember
[2],[3]      
Accumulated Depreciation (106,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21267SmithSwitchRoadMember
[4]      
21271 Smith Switch Road        
Initial Cost        
Land 7,346,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21271SmithSwitchRoadMember
     
Building and Land Improvements 16,864,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21271SmithSwitchRoadMember
     
Gross Amounts Carried at Close of Period        
Land 7,346,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21271SmithSwitchRoadMember
     
Building and Land Improvements 16,864,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21271SmithSwitchRoadMember
     
Total 24,210,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21271SmithSwitchRoadMember
[2],[3]      
Accumulated Depreciation (447,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number21271SmithSwitchRoadMember
[4]      
22289 Exploration Drive        
Initial Cost        
Land 1,422,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22289ExplorationDriveMember
     
Building and Land Improvements 5,719,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22289ExplorationDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,511,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22289ExplorationDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,422,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22289ExplorationDriveMember
     
Building and Land Improvements 7,230,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22289ExplorationDriveMember
     
Total 8,652,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22289ExplorationDriveMember
[2],[3]      
Accumulated Depreciation (2,512,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22289ExplorationDriveMember
[4]      
22299 Exploration Drive        
Initial Cost        
Land 1,362,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22299ExplorationDriveMember
     
Building and Land Improvements 5,791,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22299ExplorationDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,119,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22299ExplorationDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,362,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22299ExplorationDriveMember
     
Building and Land Improvements 6,910,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22299ExplorationDriveMember
     
Total 8,272,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22299ExplorationDriveMember
[2],[3]      
Accumulated Depreciation (2,433,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22299ExplorationDriveMember
[4]      
22300 Exploration Drive        
Initial Cost        
Land 1,094,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22300ExplorationDriveMember
     
Building and Land Improvements 5,038,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22300ExplorationDriveMember
     
Costs Capitalized Subsequent to Acquisition 539,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22300ExplorationDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,094,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22300ExplorationDriveMember
     
Building and Land Improvements 5,577,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22300ExplorationDriveMember
     
Total 6,671,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22300ExplorationDriveMember
[2],[3]      
Accumulated Depreciation (1,878,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22300ExplorationDriveMember
[4]      
22309 Exploration Drive        
Initial Cost        
Land 2,243,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22309ExplorationDriveMember
     
Building and Land Improvements 10,419,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22309ExplorationDriveMember
     
Costs Capitalized Subsequent to Acquisition 7,491,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22309ExplorationDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,243,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22309ExplorationDriveMember
     
Building and Land Improvements 17,910,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22309ExplorationDriveMember
     
Total 20,153,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22309ExplorationDriveMember
[2],[3]      
Accumulated Depreciation (3,999,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number22309ExplorationDriveMember
[4]      
23535 Cottonwood Parkway        
Initial Cost        
Land 692,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number23535CottonwoodParkwayMember
     
Building and Land Improvements 3,051,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number23535CottonwoodParkwayMember
     
Costs Capitalized Subsequent to Acquisition 223,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number23535CottonwoodParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 692,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number23535CottonwoodParkwayMember
     
Building and Land Improvements 3,274,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number23535CottonwoodParkwayMember
     
Total 3,966,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number23535CottonwoodParkwayMember
[2],[3]      
Accumulated Depreciation (1,066,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number23535CottonwoodParkwayMember
[4]      
2500 Riva Road        
Initial Cost        
Land 2,791,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2500RivaRoadMember
     
Building and Land Improvements 12,145,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2500RivaRoadMember
     
Costs Capitalized Subsequent to Acquisition 1,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2500RivaRoadMember
     
Gross Amounts Carried at Close of Period        
Land 2,791,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2500RivaRoadMember
     
Building and Land Improvements 12,146,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2500RivaRoadMember
     
Total 14,937,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2500RivaRoadMember
[2],[3]      
Accumulated Depreciation (4,073,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2500RivaRoadMember
[4]      
2691 Technology Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2691TechnologyDriveMember
[1]      
Initial Cost        
Land 2,098,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2691TechnologyDriveMember
     
Building and Land Improvements 17,334,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2691TechnologyDriveMember
     
Costs Capitalized Subsequent to Acquisition 5,115,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2691TechnologyDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,098,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2691TechnologyDriveMember
     
Building and Land Improvements 22,449,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2691TechnologyDriveMember
     
Total 24,547,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2691TechnologyDriveMember
[2],[3]      
Accumulated Depreciation (6,938,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2691TechnologyDriveMember
[4]      
2701 Technology Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 22,636,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2701TechnologyDriveMember
[1]      
Initial Cost        
Land 1,737,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2701TechnologyDriveMember
     
Building and Land Improvements 15,266,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2701TechnologyDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,554,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2701TechnologyDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,737,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2701TechnologyDriveMember
     
Building and Land Improvements 17,820,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2701TechnologyDriveMember
     
Total 19,557,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2701TechnologyDriveMember
[2],[3]      
Accumulated Depreciation (6,641,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2701TechnologyDriveMember
[4]      
2711 Technology Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 17,606,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2711TechnologyDriveMember
[1]      
Initial Cost        
Land 2,251,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2711TechnologyDriveMember
     
Building and Land Improvements 21,611,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2711TechnologyDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,451,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2711TechnologyDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,251,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2711TechnologyDriveMember
     
Building and Land Improvements 23,062,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2711TechnologyDriveMember
     
Total 25,313,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2711TechnologyDriveMember
[2],[3]      
Accumulated Depreciation (9,531,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2711TechnologyDriveMember
[4]      
2720 Technology Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2720TechnologyDriveMember
[1]      
Initial Cost        
Land 3,863,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2720TechnologyDriveMember
     
Building and Land Improvements 29,272,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2720TechnologyDriveMember
     
Costs Capitalized Subsequent to Acquisition 113,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2720TechnologyDriveMember
     
Gross Amounts Carried at Close of Period        
Land 3,863,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2720TechnologyDriveMember
     
Building and Land Improvements 29,385,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2720TechnologyDriveMember
     
Total 33,248,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2720TechnologyDriveMember
[2],[3]      
Accumulated Depreciation (7,577,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2720TechnologyDriveMember
[4]      
2721 Technology Drive        
Initial Cost        
Land 4,611,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2721TechnologyDriveMember
     
Building and Land Improvements 14,597,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2721TechnologyDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,226,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2721TechnologyDriveMember
     
Gross Amounts Carried at Close of Period        
Land 4,611,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2721TechnologyDriveMember
     
Building and Land Improvements 15,823,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2721TechnologyDriveMember
     
Total 20,434,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2721TechnologyDriveMember
[2],[3]      
Accumulated Depreciation (5,840,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2721TechnologyDriveMember
[4]      
2730 Hercules Road        
Real Estate and Accumulated Depreciation        
Encumbrances 35,161,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2730HerculesRoadMember
[1]      
Initial Cost        
Land 8,737,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2730HerculesRoadMember
     
Building and Land Improvements 31,612,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2730HerculesRoadMember
     
Costs Capitalized Subsequent to Acquisition 7,093,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2730HerculesRoadMember
     
Gross Amounts Carried at Close of Period        
Land 8,737,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2730HerculesRoadMember
     
Building and Land Improvements 38,705,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2730HerculesRoadMember
     
Total 47,442,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2730HerculesRoadMember
[2],[3]      
Accumulated Depreciation (14,268,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2730HerculesRoadMember
[4]      
2900 Towerview Road        
Initial Cost        
Land 3,207,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2900TowerviewRoadMember
     
Building and Land Improvements 16,379,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2900TowerviewRoadMember
     
Costs Capitalized Subsequent to Acquisition 6,419,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2900TowerviewRoadMember
     
Gross Amounts Carried at Close of Period        
Land 3,207,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2900TowerviewRoadMember
     
Building and Land Improvements 22,798,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2900TowerviewRoadMember
     
Total 26,005,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2900TowerviewRoadMember
[2],[3]      
Accumulated Depreciation (5,969,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number2900TowerviewRoadMember
[4]      
300 Sentinel Drive        
Initial Cost        
Land 1,517,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number300SentinelDriveMember
     
Building and Land Improvements 58,827,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number300SentinelDriveMember
     
Costs Capitalized Subsequent to Acquisition 166,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number300SentinelDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,517,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number300SentinelDriveMember
     
Building and Land Improvements 58,993,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number300SentinelDriveMember
     
Total 60,510,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number300SentinelDriveMember
[2],[3]      
Accumulated Depreciation (6,977,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number300SentinelDriveMember
[4]      
302 Sentinel Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number302SentinelDriveMember
[1]      
Initial Cost        
Land 2,648,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number302SentinelDriveMember
     
Building and Land Improvements 29,687,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number302SentinelDriveMember
     
Costs Capitalized Subsequent to Acquisition 423,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number302SentinelDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,648,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number302SentinelDriveMember
     
Building and Land Improvements 30,110,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number302SentinelDriveMember
     
Total 32,758,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number302SentinelDriveMember
[2],[3]      
Accumulated Depreciation (5,210,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number302SentinelDriveMember
[4]      
304 Sentinel Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number304SentinelDriveMember
[1]      
Initial Cost        
Land 3,411,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number304SentinelDriveMember
     
Building and Land Improvements 24,917,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number304SentinelDriveMember
     
Costs Capitalized Subsequent to Acquisition 138,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number304SentinelDriveMember
     
Gross Amounts Carried at Close of Period        
Land 3,411,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number304SentinelDriveMember
     
Building and Land Improvements 25,055,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number304SentinelDriveMember
     
Total 28,466,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number304SentinelDriveMember
[2],[3]      
Accumulated Depreciation (5,655,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number304SentinelDriveMember
[4]      
306 Sentinel Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 16,298,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number306SentinelDriveMember
[1]      
Initial Cost        
Land 3,260,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number306SentinelDriveMember
     
Building and Land Improvements 22,592,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number306SentinelDriveMember
     
Costs Capitalized Subsequent to Acquisition 415,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number306SentinelDriveMember
     
Gross Amounts Carried at Close of Period        
Land 3,260,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number306SentinelDriveMember
     
Building and Land Improvements 23,007,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number306SentinelDriveMember
     
Total 26,267,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number306SentinelDriveMember
[2],[3]      
Accumulated Depreciation (4,687,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number306SentinelDriveMember
[4]      
308 Sentinel Drive        
Initial Cost        
Land 1,422,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number308SentinelDriveMember
     
Building and Land Improvements 26,197,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number308SentinelDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,422,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number308SentinelDriveMember
     
Building and Land Improvements 26,197,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number308SentinelDriveMember
     
Total 27,619,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number308SentinelDriveMember
[2],[3]      
Accumulated Depreciation (2,395,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number308SentinelDriveMember
[4]      
310 Sentinel Way        
Initial Cost        
Land 2,372,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310SentinelWayMember
[5]      
Building and Land Improvements 33,953,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310SentinelWayMember
[5]      
Gross Amounts Carried at Close of Period        
Land 2,372,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310SentinelWayMember
[5]      
Building and Land Improvements 33,953,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310SentinelWayMember
[5]      
Total 36,325,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310SentinelWayMember
[2],[3],[5]      
Accumulated Depreciation 0us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310SentinelWayMember
[4],[5]      
310 The Bridge Street        
Initial Cost        
Land 261,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310BridgeStreetMember
     
Building and Land Improvements 26,531,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310BridgeStreetMember
     
Costs Capitalized Subsequent to Acquisition 1,051,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310BridgeStreetMember
     
Gross Amounts Carried at Close of Period        
Land 261,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310BridgeStreetMember
     
Building and Land Improvements 27,582,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310BridgeStreetMember
     
Total 27,843,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310BridgeStreetMember
[2],[3]      
Accumulated Depreciation (4,310,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number310BridgeStreetMember
[4]      
312 Sentinel Way        
Initial Cost        
Land 3,138,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number312SentinelWayMember
     
Building and Land Improvements 23,793,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number312SentinelWayMember
     
Gross Amounts Carried at Close of Period        
Land 3,138,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number312SentinelWayMember
     
Building and Land Improvements 23,793,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number312SentinelWayMember
     
Total 26,931,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number312SentinelWayMember
[2],[3]      
Accumulated Depreciation (240,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number312SentinelWayMember
[4]      
3120 Fairview Park Drive        
Initial Cost        
Land 6,863,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number3120FairviewParkDriveMember
     
Building and Land Improvements 35,606,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number3120FairviewParkDriveMember
     
Costs Capitalized Subsequent to Acquisition 7,303,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number3120FairviewParkDriveMember
     
Gross Amounts Carried at Close of Period        
Land 6,863,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number3120FairviewParkDriveMember
     
Building and Land Improvements 42,909,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number3120FairviewParkDriveMember
     
Total 49,772,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number3120FairviewParkDriveMember
[2],[3]      
Accumulated Depreciation (5,456,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number3120FairviewParkDriveMember
[4]      
314 Sentinel Way        
Initial Cost        
Land 1,254,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number314SentinelWayMember
     
Building and Land Improvements 1,325,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number314SentinelWayMember
     
Gross Amounts Carried at Close of Period        
Land 1,254,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number314SentinelWayMember
     
Building and Land Improvements 1,325,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number314SentinelWayMember
     
Total 2,579,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number314SentinelWayMember
[2],[3]      
Accumulated Depreciation (216,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number314SentinelWayMember
[4]      
316 Sentinel Way        
Initial Cost        
Land 2,748,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number316SentinelWayMember
     
Building and Land Improvements 38,156,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number316SentinelWayMember
     
Costs Capitalized Subsequent to Acquisition 139,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number316SentinelWayMember
     
Gross Amounts Carried at Close of Period        
Land 2,748,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number316SentinelWayMember
     
Building and Land Improvements 38,295,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number316SentinelWayMember
     
Total 41,043,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number316SentinelWayMember
[2],[3]      
Accumulated Depreciation (2,602,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number316SentinelWayMember
[4]      
318 Sentinel Way        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number318SentinelWayMember
[1]      
Initial Cost        
Land 2,185,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number318SentinelWayMember
     
Building and Land Improvements 28,426,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number318SentinelWayMember
     
Gross Amounts Carried at Close of Period        
Land 2,185,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number318SentinelWayMember
     
Building and Land Improvements 28,426,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number318SentinelWayMember
     
Total 30,611,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number318SentinelWayMember
[2],[3]      
Accumulated Depreciation (6,270,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number318SentinelWayMember
[4]      
320 Sentinel Way        
Initial Cost        
Land 2,067,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number320SentinelWayMember
     
Building and Land Improvements 21,623,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number320SentinelWayMember
     
Gross Amounts Carried at Close of Period        
Land 2,067,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number320SentinelWayMember
     
Building and Land Improvements 21,623,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number320SentinelWayMember
     
Total 23,690,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number320SentinelWayMember
[2],[3]      
Accumulated Depreciation (3,770,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number320SentinelWayMember
[4]      
322 Sentinel Way        
Real Estate and Accumulated Depreciation        
Encumbrances 21,680,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number322SentinelWayMember
[1]      
Initial Cost        
Land 2,605,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number322SentinelWayMember
     
Building and Land Improvements 22,827,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number322SentinelWayMember
     
Gross Amounts Carried at Close of Period        
Land 2,605,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number322SentinelWayMember
     
Building and Land Improvements 22,827,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number322SentinelWayMember
     
Total 25,432,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number322SentinelWayMember
[2],[3]      
Accumulated Depreciation (4,572,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number322SentinelWayMember
[4]      
324 Sentinel Way        
Initial Cost        
Land 1,656,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number324SentinelWayMember
     
Building and Land Improvements 23,018,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number324SentinelWayMember
     
Gross Amounts Carried at Close of Period        
Land 1,656,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number324SentinelWayMember
     
Building and Land Improvements 23,018,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number324SentinelWayMember
     
Total 24,674,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number324SentinelWayMember
[2],[3]      
Accumulated Depreciation (2,503,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number324SentinelWayMember
[4]      
375 West Padonia Road        
Initial Cost        
Land 2,483,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number375WestPadoniaRoadMember
     
Building and Land Improvements 10,415,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number375WestPadoniaRoadMember
     
Costs Capitalized Subsequent to Acquisition 4,857,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number375WestPadoniaRoadMember
     
Gross Amounts Carried at Close of Period        
Land 2,483,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number375WestPadoniaRoadMember
     
Building and Land Improvements 15,272,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number375WestPadoniaRoadMember
     
Total 17,755,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number375WestPadoniaRoadMember
[2],[3]      
Accumulated Depreciation (6,904,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number375WestPadoniaRoadMember
[4]      
410 National Business Parkway        
Initial Cost        
Land 1,831,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number410NationalBusinessParkwayMember
     
Building and Land Improvements 23,257,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number410NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 112,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number410NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 1,831,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number410NationalBusinessParkwayMember
     
Building and Land Improvements 23,369,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number410NationalBusinessParkwayMember
     
Total 25,200,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number410NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (1,127,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number410NationalBusinessParkwayMember
[4]      
420 National Business Parkway        
Initial Cost        
Land 2,370,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number420NationalBusinessParkwayMember
     
Building and Land Improvements 27,161,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number420NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 101,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number420NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 2,370,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number420NationalBusinessParkwayMember
     
Building and Land Improvements 27,262,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number420NationalBusinessParkwayMember
     
Total 29,632,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number420NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (541,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number420NationalBusinessParkwayMember
[4]      
430 National Business Parkway        
Initial Cost        
Land 1,852,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number430NationalBusinessParkwayMember
     
Building and Land Improvements 21,138,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number430NationalBusinessParkwayMember
     
Costs Capitalized Subsequent to Acquisition 120,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number430NationalBusinessParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 1,852,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number430NationalBusinessParkwayMember
     
Building and Land Improvements 21,258,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number430NationalBusinessParkwayMember
     
Total 23,110,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number430NationalBusinessParkwayMember
[2],[3]      
Accumulated Depreciation (1,494,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number430NationalBusinessParkwayMember
[4]      
44408 Pecan Court        
Initial Cost        
Land 817,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44408PecanCourtMember
     
Building and Land Improvements 1,583,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44408PecanCourtMember
     
Costs Capitalized Subsequent to Acquisition 582,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44408PecanCourtMember
     
Gross Amounts Carried at Close of Period        
Land 817,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44408PecanCourtMember
     
Building and Land Improvements 2,165,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44408PecanCourtMember
     
Total 2,982,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44408PecanCourtMember
[2],[3]      
Accumulated Depreciation (405,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44408PecanCourtMember
[4]      
44414 Pecan Court        
Initial Cost        
Land 405,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44414PecanCourtMember
     
Building and Land Improvements 1,619,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44414PecanCourtMember
     
Costs Capitalized Subsequent to Acquisition 336,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44414PecanCourtMember
     
Gross Amounts Carried at Close of Period        
Land 405,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44414PecanCourtMember
     
Building and Land Improvements 1,955,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44414PecanCourtMember
     
Total 2,360,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44414PecanCourtMember
[2],[3]      
Accumulated Depreciation (641,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44414PecanCourtMember
[4]      
44417 Pecan Court        
Initial Cost        
Land 434,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44417PecanCourtMember
[5]      
Building and Land Improvements 3,204,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44417PecanCourtMember
[5]      
Costs Capitalized Subsequent to Acquisition 88,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44417PecanCourtMember
[5]      
Gross Amounts Carried at Close of Period        
Land 434,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44417PecanCourtMember
[5]      
Building and Land Improvements 3,292,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44417PecanCourtMember
[5]      
Total 3,726,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44417PecanCourtMember
[2],[3],[5]      
Accumulated Depreciation (1,037,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44417PecanCourtMember
[4],[5]      
44420 Pecan Court        
Initial Cost        
Land 344,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44420PecanCourtMember
     
Building and Land Improvements 890,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44420PecanCourtMember
     
Costs Capitalized Subsequent to Acquisition 148,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44420PecanCourtMember
     
Gross Amounts Carried at Close of Period        
Land 344,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44420PecanCourtMember
     
Building and Land Improvements 1,038,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44420PecanCourtMember
     
Total 1,382,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44420PecanCourtMember
[2],[3]      
Accumulated Depreciation (199,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44420PecanCourtMember
[4]      
44425 Pecan Court        
Initial Cost        
Land 1,309,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44425PecanCourtMember
     
Building and Land Improvements 3,506,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44425PecanCourtMember
     
Costs Capitalized Subsequent to Acquisition 1,307,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44425PecanCourtMember
     
Gross Amounts Carried at Close of Period        
Land 1,309,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44425PecanCourtMember
     
Building and Land Improvements 4,813,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44425PecanCourtMember
     
Total 6,122,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44425PecanCourtMember
[2],[3]      
Accumulated Depreciation (1,492,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number44425PecanCourtMember
[4]      
45310 Abell House Lane        
Initial Cost        
Land 2,272,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number45310AbellHouseLaneMember
     
Building and Land Improvements 13,808,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number45310AbellHouseLaneMember
     
Gross Amounts Carried at Close of Period        
Land 2,272,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number45310AbellHouseLaneMember
     
Building and Land Improvements 13,808,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number45310AbellHouseLaneMember
     
Total 16,080,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number45310AbellHouseLaneMember
[2],[3]      
Accumulated Depreciation (1,057,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number45310AbellHouseLaneMember
[4]      
46579 Expedition Drive        
Initial Cost        
Land 1,406,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46579ExpeditionDriveMember
     
Building and Land Improvements 5,796,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46579ExpeditionDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,335,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46579ExpeditionDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,406,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46579ExpeditionDriveMember
     
Building and Land Improvements 7,131,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46579ExpeditionDriveMember
     
Total 8,537,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46579ExpeditionDriveMember
[2],[3]      
Accumulated Depreciation (2,780,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46579ExpeditionDriveMember
[4]      
46591 Expedition Drive        
Initial Cost        
Land 1,200,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46591ExpeditionDriveMember
     
Building and Land Improvements 7,199,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46591ExpeditionDriveMember
     
Costs Capitalized Subsequent to Acquisition 803,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46591ExpeditionDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,200,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46591ExpeditionDriveMember
     
Building and Land Improvements 8,002,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46591ExpeditionDriveMember
     
Total 9,202,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46591ExpeditionDriveMember
[2],[3]      
Accumulated Depreciation (1,618,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number46591ExpeditionDriveMember
[4]      
4851 Stonecroft Boulevard        
Initial Cost        
Land 1,878,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4851StonecroftBoulevardMember
     
Building and Land Improvements 11,558,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4851StonecroftBoulevardMember
     
Costs Capitalized Subsequent to Acquisition 21,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4851StonecroftBoulevardMember
     
Gross Amounts Carried at Close of Period        
Land 1,878,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4851StonecroftBoulevardMember
     
Building and Land Improvements 11,579,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4851StonecroftBoulevardMember
     
Total 13,457,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4851StonecroftBoulevardMember
[2],[3]      
Accumulated Depreciation (2,959,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4851StonecroftBoulevardMember
[4]      
4940 Campbell Drive        
Initial Cost        
Land 1,379,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4940CampbellDriveMember
     
Building and Land Improvements 3,858,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4940CampbellDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,373,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4940CampbellDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,379,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4940CampbellDriveMember
     
Building and Land Improvements 5,231,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4940CampbellDriveMember
     
Total 6,610,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4940CampbellDriveMember
[2],[3]      
Accumulated Depreciation (1,278,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number4940CampbellDriveMember
[4]      
525 Babcock Road        
Initial Cost        
Land 355,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number525BabcockRoadMember
     
Building and Land Improvements 397,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number525BabcockRoadMember
     
Costs Capitalized Subsequent to Acquisition 79,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number525BabcockRoadMember
     
Gross Amounts Carried at Close of Period        
Land 355,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number525BabcockRoadMember
     
Building and Land Improvements 476,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number525BabcockRoadMember
     
Total 831,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number525BabcockRoadMember
[2],[3]      
Accumulated Depreciation (153,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number525BabcockRoadMember
[4]      
5325 Nottingham Drive        
Initial Cost        
Land 816,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5325NottinghamDriveMember
     
Building and Land Improvements 3,976,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5325NottinghamDriveMember
     
Costs Capitalized Subsequent to Acquisition 485,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5325NottinghamDriveMember
     
Gross Amounts Carried at Close of Period        
Land 816,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5325NottinghamDriveMember
     
Building and Land Improvements 4,461,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5325NottinghamDriveMember
     
Total 5,277,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5325NottinghamDriveMember
[2],[3]      
Accumulated Depreciation (1,076,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5325NottinghamDriveMember
[4]      
5355 Nottingham Drive        
Initial Cost        
Land 761,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5355NottinghamDriveMember
     
Building and Land Improvements 3,562,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5355NottinghamDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,758,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5355NottinghamDriveMember
     
Gross Amounts Carried at Close of Period        
Land 761,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5355NottinghamDriveMember
     
Building and Land Improvements 5,320,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5355NottinghamDriveMember
     
Total 6,081,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5355NottinghamDriveMember
[2],[3]      
Accumulated Depreciation (1,874,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5355NottinghamDriveMember
[4]      
5520 Research Park Drive        
Initial Cost        
Building and Land Improvements 20,072,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5520ResearchParkDriveMember
     
Costs Capitalized Subsequent to Acquisition 38,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5520ResearchParkDriveMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 20,110,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5520ResearchParkDriveMember
     
Total 20,110,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5520ResearchParkDriveMember
[2],[3]      
Accumulated Depreciation (2,687,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5520ResearchParkDriveMember
[4]      
5522 Research Park Drive        
Initial Cost        
Building and Land Improvements 4,550,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5522ResearchParkDriveMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 4,550,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5522ResearchParkDriveMember
     
Total 4,550,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5522ResearchParkDriveMember
[2],[3]      
Accumulated Depreciation (842,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5522ResearchParkDriveMember
[4]      
5825 University Research Court        
Real Estate and Accumulated Depreciation        
Encumbrances 15,615,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5825UniversityResearchCourtMember
[1]      
Initial Cost        
Building and Land Improvements 22,522,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5825UniversityResearchCourtMember
     
Costs Capitalized Subsequent to Acquisition 60,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5825UniversityResearchCourtMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 22,582,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5825UniversityResearchCourtMember
     
Total 22,582,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5825UniversityResearchCourtMember
[2],[3]      
Accumulated Depreciation (3,246,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5825UniversityResearchCourtMember
[4]      
5850 University Research Court        
Real Estate and Accumulated Depreciation        
Encumbrances 21,261,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5850UniversityResearchCourtMember
[1]      
Initial Cost        
Building and Land Improvements 31,689,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5850UniversityResearchCourtMember
     
Costs Capitalized Subsequent to Acquisition 57,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5850UniversityResearchCourtMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 31,746,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5850UniversityResearchCourtMember
     
Total 31,746,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5850UniversityResearchCourtMember
[2],[3]      
Accumulated Depreciation (3,763,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number5850UniversityResearchCourtMember
[4]      
6700 Alexander Bell Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6700AlexanderBellDriveMember
[1]      
Initial Cost        
Land 1,755,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6700AlexanderBellDriveMember
     
Building and Land Improvements 7,019,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6700AlexanderBellDriveMember
     
Costs Capitalized Subsequent to Acquisition 5,550,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6700AlexanderBellDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,755,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6700AlexanderBellDriveMember
     
Building and Land Improvements 12,569,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6700AlexanderBellDriveMember
     
Total 14,324,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6700AlexanderBellDriveMember
[2],[3]      
Accumulated Depreciation (5,435,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6700AlexanderBellDriveMember
[4]      
6708 Alexander Bell Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6708AlexanderBellDriveMember
[1],[5]      
Initial Cost        
Land 897,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6708AlexanderBellDriveMember
[5]      
Building and Land Improvements 7,544,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6708AlexanderBellDriveMember
[5]      
Costs Capitalized Subsequent to Acquisition 1,591,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6708AlexanderBellDriveMember
[5]      
Gross Amounts Carried at Close of Period        
Land 897,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6708AlexanderBellDriveMember
[5]      
Building and Land Improvements 9,135,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6708AlexanderBellDriveMember
[5]      
Total 10,032,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6708AlexanderBellDriveMember
[2],[3],[5]      
Accumulated Depreciation (3,319,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6708AlexanderBellDriveMember
[4],[5]      
6711 Columbia Gateway Drive        
Initial Cost        
Land 2,683,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6711ColumbiaGatewayDriveMember
     
Building and Land Improvements 23,239,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6711ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 435,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6711ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,683,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6711ColumbiaGatewayDriveMember
     
Building and Land Improvements 23,674,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6711ColumbiaGatewayDriveMember
     
Total 26,357,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6711ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (4,765,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6711ColumbiaGatewayDriveMember
[4]      
6716 Alexander Bell Drive        
Initial Cost        
Land 1,242,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6716AlexanderBellDriveMember
     
Building and Land Improvements 4,969,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6716AlexanderBellDriveMember
     
Costs Capitalized Subsequent to Acquisition 3,352,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6716AlexanderBellDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,242,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6716AlexanderBellDriveMember
     
Building and Land Improvements 8,321,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6716AlexanderBellDriveMember
     
Total 9,563,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6716AlexanderBellDriveMember
[2],[3]      
Accumulated Depreciation (3,992,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6716AlexanderBellDriveMember
[4]      
6721 Columbia Gateway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 17,102,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6721ColumbiaGatewayDriveMember
[1]      
Initial Cost        
Land 1,753,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6721ColumbiaGatewayDriveMember
     
Building and Land Improvements 34,090,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6721ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 65,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6721ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,753,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6721ColumbiaGatewayDriveMember
     
Building and Land Improvements 34,155,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6721ColumbiaGatewayDriveMember
     
Total 35,908,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6721ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (4,941,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6721ColumbiaGatewayDriveMember
[4]      
6724 Alexander Bell Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6724AlexanderBellDriveMember
[1]      
Initial Cost        
Land 449,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6724AlexanderBellDriveMember
     
Building and Land Improvements 5,039,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6724AlexanderBellDriveMember
     
Costs Capitalized Subsequent to Acquisition 368,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6724AlexanderBellDriveMember
     
Gross Amounts Carried at Close of Period        
Land 449,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6724AlexanderBellDriveMember
     
Building and Land Improvements 5,407,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6724AlexanderBellDriveMember
     
Total 5,856,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6724AlexanderBellDriveMember
[2],[3]      
Accumulated Depreciation (2,106,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6724AlexanderBellDriveMember
[4]      
6731 Columbia Gateway Drive        
Initial Cost        
Land 2,807,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6731ColumbiaGatewayDriveMember
     
Building and Land Improvements 19,098,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6731ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,046,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6731ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,807,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6731ColumbiaGatewayDriveMember
     
Building and Land Improvements 21,144,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6731ColumbiaGatewayDriveMember
     
Total 23,951,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6731ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (7,841,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6731ColumbiaGatewayDriveMember
[4]      
6740 Alexander Bell Drive        
Initial Cost        
Land 1,424,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6740AlexanderBellDriveMember
     
Building and Land Improvements 5,696,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6740AlexanderBellDriveMember
     
Costs Capitalized Subsequent to Acquisition 3,346,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6740AlexanderBellDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,424,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6740AlexanderBellDriveMember
     
Building and Land Improvements 9,042,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6740AlexanderBellDriveMember
     
Total 10,466,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6740AlexanderBellDriveMember
[2],[3]      
Accumulated Depreciation (4,644,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6740AlexanderBellDriveMember
[4]      
6741 Columbia Gateway Drive        
Initial Cost        
Land 675,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6741ColumbiaGatewayDriveMember
     
Building and Land Improvements 1,711,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6741ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 114,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6741ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 675,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6741ColumbiaGatewayDriveMember
     
Building and Land Improvements 1,825,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6741ColumbiaGatewayDriveMember
     
Total 2,500,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6741ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (303,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6741ColumbiaGatewayDriveMember
[4]      
6750 Alexander Bell Drive        
Initial Cost        
Land 1,263,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6750AlexanderBellDriveMember
     
Building and Land Improvements 12,461,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6750AlexanderBellDriveMember
     
Costs Capitalized Subsequent to Acquisition 3,419,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6750AlexanderBellDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,263,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6750AlexanderBellDriveMember
     
Building and Land Improvements 15,880,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6750AlexanderBellDriveMember
     
Total 17,143,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6750AlexanderBellDriveMember
[2],[3]      
Accumulated Depreciation (7,008,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6750AlexanderBellDriveMember
[4]      
6760 Alexander Bell Drive        
Initial Cost        
Land 890,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6760AlexanderBellDriveMember
     
Building and Land Improvements 3,561,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6760AlexanderBellDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,763,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6760AlexanderBellDriveMember
     
Gross Amounts Carried at Close of Period        
Land 890,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6760AlexanderBellDriveMember
     
Building and Land Improvements 6,324,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6760AlexanderBellDriveMember
     
Total 7,214,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6760AlexanderBellDriveMember
[2],[3]      
Accumulated Depreciation (2,989,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6760AlexanderBellDriveMember
[4]      
6940 Columbia Gateway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6940ColumbiaGatewayDriveMember
[1]      
Initial Cost        
Land 3,545,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6940ColumbiaGatewayDriveMember
     
Building and Land Improvements 9,916,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6940ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 4,717,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6940ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 3,545,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6940ColumbiaGatewayDriveMember
     
Building and Land Improvements 14,633,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6940ColumbiaGatewayDriveMember
     
Total 18,178,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6940ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (6,463,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6940ColumbiaGatewayDriveMember
[4]      
6950 Columbia Gateway Drive        
Initial Cost        
Land 3,596,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6950ColumbiaGatewayDriveMember
     
Building and Land Improvements 14,269,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6950ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,164,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6950ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 3,596,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6950ColumbiaGatewayDriveMember
     
Building and Land Improvements 16,433,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6950ColumbiaGatewayDriveMember
     
Total 20,029,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6950ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (6,965,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number6950ColumbiaGatewayDriveMember
[4]      
7000 Columbia Gateway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7000ColumbiaGatewayDriveMember
[1]      
Initial Cost        
Land 3,131,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7000ColumbiaGatewayDriveMember
     
Building and Land Improvements 12,103,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7000ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 989,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7000ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 3,131,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7000ColumbiaGatewayDriveMember
     
Building and Land Improvements 13,092,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7000ColumbiaGatewayDriveMember
     
Total 16,223,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7000ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (4,056,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7000ColumbiaGatewayDriveMember
[4]      
7005 Columbia Gateway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7005ColumbiaGatewayDriveMember
[1],[6]      
Initial Cost        
Land 3,036,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7005ColumbiaGatewayDriveMember
[6]      
Building and Land Improvements 14,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7005ColumbiaGatewayDriveMember
[6]      
Costs Capitalized Subsequent to Acquisition 0us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7005ColumbiaGatewayDriveMember
[6]      
Gross Amounts Carried at Close of Period        
Land 3,036,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7005ColumbiaGatewayDriveMember
[6]      
Building and Land Improvements 14,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7005ColumbiaGatewayDriveMember
[6]      
Total 3,050,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7005ColumbiaGatewayDriveMember
[2],[3],[6]      
Accumulated Depreciation 0us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7005ColumbiaGatewayDriveMember
[4],[6]      
7015 Albert Einstein Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 1,900,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7015AlbertEinsteinDriveMember
[1]      
Initial Cost        
Land 2,058,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7015AlbertEinsteinDriveMember
     
Building and Land Improvements 6,093,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7015AlbertEinsteinDriveMember
     
Costs Capitalized Subsequent to Acquisition 855,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7015AlbertEinsteinDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,058,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7015AlbertEinsteinDriveMember
     
Building and Land Improvements 6,948,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7015AlbertEinsteinDriveMember
     
Total 9,006,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7015AlbertEinsteinDriveMember
[2],[3]      
Accumulated Depreciation (2,669,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7015AlbertEinsteinDriveMember
[4]      
7061 Columbia Gateway Drive        
Initial Cost        
Land 729,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7061ColumbiaGatewayDriveMember
     
Building and Land Improvements 3,094,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7061ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,407,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7061ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 729,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7061ColumbiaGatewayDriveMember
     
Building and Land Improvements 4,501,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7061ColumbiaGatewayDriveMember
     
Total 5,230,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7061ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (1,657,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7061ColumbiaGatewayDriveMember
[4]      
7063 Columbia Gateway Drive        
Initial Cost        
Land 902,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7063ColumbiaGatewayDriveMember
     
Building and Land Improvements 3,684,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7063ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,074,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7063ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 902,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7063ColumbiaGatewayDriveMember
     
Building and Land Improvements 4,758,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7063ColumbiaGatewayDriveMember
     
Total 5,660,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7063ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (2,272,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7063ColumbiaGatewayDriveMember
[4]      
7065 Columbia Gateway Drive        
Initial Cost        
Land 919,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7065ColumbiaGatewayDriveMember
     
Building and Land Improvements 3,763,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7065ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,902,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7065ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 919,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7065ColumbiaGatewayDriveMember
     
Building and Land Improvements 6,665,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7065ColumbiaGatewayDriveMember
     
Total 7,584,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7065ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (2,343,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7065ColumbiaGatewayDriveMember
[4]      
7067 Columbia Gateway Drive        
Initial Cost        
Land 1,829,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7067ColumbiaGatewayDriveMember
     
Building and Land Improvements 11,823,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7067ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,773,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7067ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,829,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7067ColumbiaGatewayDriveMember
     
Building and Land Improvements 14,596,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7067ColumbiaGatewayDriveMember
     
Total 16,425,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7067ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (5,461,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7067ColumbiaGatewayDriveMember
[4]      
7125 Columbia Gateway Drive Land        
Initial Cost        
Land 3,361,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveLandMember
[6]      
Building and Land Improvements 555,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveLandMember
[6]      
Costs Capitalized Subsequent to Acquisition 279,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveLandMember
[6]      
Gross Amounts Carried at Close of Period        
Land 3,361,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveLandMember
[6]      
Building and Land Improvements 834,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveLandMember
[6]      
Total 4,195,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveLandMember
[2],[3],[6]      
7125 Columbia Gateway Drive        
Initial Cost        
Land 17,126,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveMember
     
Building and Land Improvements 46,994,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 8,848,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 17,126,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveMember
     
Building and Land Improvements 55,842,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveMember
     
Total 72,968,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (14,434,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7125ColumbiaGatewayDriveMember
[4]      
7130 Columbia Gateway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7130ColumbiaGatewayDriveMember
[1]      
Initial Cost        
Land 1,350,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7130ColumbiaGatewayDriveMember
     
Building and Land Improvements 4,359,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7130ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,802,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7130ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,350,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7130ColumbiaGatewayDriveMember
     
Building and Land Improvements 6,161,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7130ColumbiaGatewayDriveMember
     
Total 7,511,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7130ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (2,321,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7130ColumbiaGatewayDriveMember
[4]      
7134 Columbia Gateway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7134ColumbiaGatewayDriveMember
[1]      
Initial Cost        
Land 704,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7134ColumbiaGatewayDriveMember
     
Building and Land Improvements 1,971,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7134ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 310,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7134ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 704,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7134ColumbiaGatewayDriveMember
     
Building and Land Improvements 2,281,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7134ColumbiaGatewayDriveMember
     
Total 2,985,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7134ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (638,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7134ColumbiaGatewayDriveMember
[4]      
7138 Columbia Gateway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7138ColumbiaGatewayDriveMember
[1]      
Initial Cost        
Land 1,104,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7138ColumbiaGatewayDriveMember
     
Building and Land Improvements 3,518,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7138ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,975,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7138ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,104,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7138ColumbiaGatewayDriveMember
     
Building and Land Improvements 5,493,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7138ColumbiaGatewayDriveMember
     
Total 6,597,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7138ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (2,817,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7138ColumbiaGatewayDriveMember
[4]      
7142 Columbia Gateway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7142ColumbiaGatewayDriveMember
[1]      
Initial Cost        
Land 1,342,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7142ColumbiaGatewayDriveMember
     
Building and Land Improvements 3,978,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7142ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,494,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7142ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,342,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7142ColumbiaGatewayDriveMember
     
Building and Land Improvements 6,472,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7142ColumbiaGatewayDriveMember
     
Total 7,814,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7142ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (2,091,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7142ColumbiaGatewayDriveMember
[4]      
7150 Columbia Gateway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150ColumbiaGatewayDriveMember
[1]      
Initial Cost        
Land 1,032,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150ColumbiaGatewayDriveMember
     
Building and Land Improvements 3,429,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150ColumbiaGatewayDriveMember
     
Costs Capitalized Subsequent to Acquisition 579,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150ColumbiaGatewayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,032,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150ColumbiaGatewayDriveMember
     
Building and Land Improvements 4,008,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150ColumbiaGatewayDriveMember
     
Total 5,040,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150ColumbiaGatewayDriveMember
[2],[3]      
Accumulated Depreciation (1,056,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150ColumbiaGatewayDriveMember
[4]      
7150 Riverwood Drive        
Initial Cost        
Land 1,821,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150RiverwoodDriveMember
     
Building and Land Improvements 4,388,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150RiverwoodDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,332,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150RiverwoodDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,821,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150RiverwoodDriveMember
     
Building and Land Improvements 5,720,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150RiverwoodDriveMember
     
Total 7,541,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150RiverwoodDriveMember
[2],[3]      
Accumulated Depreciation (1,742,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7150RiverwoodDriveMember
[4]      
7160 Riverwood Drive        
Initial Cost        
Land 2,732,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7160RiverwoodDriveMember
     
Building and Land Improvements 7,006,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7160RiverwoodDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,605,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7160RiverwoodDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,732,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7160RiverwoodDriveMember
     
Building and Land Improvements 8,611,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7160RiverwoodDriveMember
     
Total 11,343,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7160RiverwoodDriveMember
[2],[3]      
Accumulated Depreciation (3,040,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7160RiverwoodDriveMember
[4]      
7170 Riverwood Drive        
Initial Cost        
Land 1,283,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7170RiverwoodDriveMember
     
Building and Land Improvements 3,096,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7170RiverwoodDriveMember
     
Costs Capitalized Subsequent to Acquisition 658,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7170RiverwoodDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,283,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7170RiverwoodDriveMember
     
Building and Land Improvements 3,754,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7170RiverwoodDriveMember
     
Total 5,037,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7170RiverwoodDriveMember
[2],[3]      
Accumulated Depreciation (1,218,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7170RiverwoodDriveMember
[4]      
7175 Riverwood Drive        
Initial Cost        
Land 1,788,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7175RiverwoodDriveMember
     
Building and Land Improvements 7,270,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7175RiverwoodDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,788,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7175RiverwoodDriveMember
     
Building and Land Improvements 7,270,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7175RiverwoodDriveMember
     
Total 9,058,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7175RiverwoodDriveMember
[2],[3]      
Accumulated Depreciation (207,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7175RiverwoodDriveMember
[4]      
7200 Redstone Gateway        
Initial Cost        
Building and Land Improvements 4,926,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RedstoneGatewayMemberMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 4,926,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RedstoneGatewayMemberMember
     
Total 4,926,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RedstoneGatewayMemberMember
[2],[3]      
Accumulated Depreciation (133,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RedstoneGatewayMemberMember
[4]      
7200 Riverwood Road        
Initial Cost        
Land 4,089,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RiverwoodRoadMember
     
Building and Land Improvements 16,356,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RiverwoodRoadMember
     
Costs Capitalized Subsequent to Acquisition 3,538,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RiverwoodRoadMember
     
Gross Amounts Carried at Close of Period        
Land 4,089,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RiverwoodRoadMember
     
Building and Land Improvements 19,894,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RiverwoodRoadMember
     
Total 23,983,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RiverwoodRoadMember
[2],[3]      
Accumulated Depreciation (7,933,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7200RiverwoodRoadMember
[4]      
7205 Riverwood Drive        
Initial Cost        
Land 1,367,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7205RiverwoodDriveMember
     
Building and Land Improvements 24,114,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7205RiverwoodDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,367,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7205RiverwoodDriveMember
     
Building and Land Improvements 24,114,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7205RiverwoodDriveMember
     
Total 25,481,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7205RiverwoodDriveMember
[2],[3]      
Accumulated Depreciation (774,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7205RiverwoodDriveMember
[4]      
7272 Park Circle Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 4,919,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7272ParkCircleDriveMember
[1]      
Initial Cost        
Land 1,479,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7272ParkCircleDriveMember
     
Building and Land Improvements 6,300,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7272ParkCircleDriveMember
     
Costs Capitalized Subsequent to Acquisition 3,884,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7272ParkCircleDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,479,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7272ParkCircleDriveMember
     
Building and Land Improvements 10,184,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7272ParkCircleDriveMember
     
Total 11,663,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7272ParkCircleDriveMember
[2],[3]      
Accumulated Depreciation (2,461,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7272ParkCircleDriveMember
[4]      
7318 Parkway Drive        
Initial Cost        
Land 972,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7318ParkwayDriveMember
     
Building and Land Improvements 3,888,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7318ParkwayDriveMember
     
Costs Capitalized Subsequent to Acquisition 926,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7318ParkwayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 972,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7318ParkwayDriveMember
     
Building and Land Improvements 4,814,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7318ParkwayDriveMember
     
Total 5,786,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7318ParkwayDriveMember
[2],[3]      
Accumulated Depreciation (1,879,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7318ParkwayDriveMember
[4]      
7320 Parkway Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7320ParkwayDriveMember
[1]      
Initial Cost        
Land 905,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7320ParkwayDriveMember
     
Building and Land Improvements 3,570,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7320ParkwayDriveMember
     
Costs Capitalized Subsequent to Acquisition 4,018,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7320ParkwayDriveMember
     
Gross Amounts Carried at Close of Period        
Land 905,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7320ParkwayDriveMember
     
Building and Land Improvements 7,588,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7320ParkwayDriveMember
     
Total 8,493,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7320ParkwayDriveMember
[2],[3]      
Accumulated Depreciation (2,310,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7320ParkwayDriveMember
[4]      
7400 Redstone Gateway        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7400RedstoneGatewayMember
[1],[5]      
Initial Cost        
Land 0us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7400RedstoneGatewayMember
[5]      
Building and Land Improvements 4,163,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7400RedstoneGatewayMember
[5]      
Costs Capitalized Subsequent to Acquisition 0us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7400RedstoneGatewayMember
[5]      
Gross Amounts Carried at Close of Period        
Land 0us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7400RedstoneGatewayMember
[5]      
Building and Land Improvements 4,163,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7400RedstoneGatewayMember
[5]      
Total 4,163,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7400RedstoneGatewayMember
[2],[3],[5]      
Accumulated Depreciation 0us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7400RedstoneGatewayMember
[4],[5]      
7467 Ridge Road        
Initial Cost        
Land 1,629,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7467RidgeRoadMember
     
Building and Land Improvements 6,517,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7467RidgeRoadMember
     
Costs Capitalized Subsequent to Acquisition 2,402,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7467RidgeRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,629,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7467RidgeRoadMember
     
Building and Land Improvements 8,919,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7467RidgeRoadMember
     
Total 10,548,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7467RidgeRoadMember
[2],[3]      
Accumulated Depreciation (4,138,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7467RidgeRoadMember
[4]      
7740 Milestone Parkway        
Real Estate and Accumulated Depreciation        
Encumbrances 19,357,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7740MilestoneParkwayMember
[1]      
Initial Cost        
Land 3,825,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7740MilestoneParkwayMember
     
Building and Land Improvements 34,365,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7740MilestoneParkwayMember
     
Costs Capitalized Subsequent to Acquisition 366,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7740MilestoneParkwayMember
     
Gross Amounts Carried at Close of Period        
Land 3,825,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7740MilestoneParkwayMember
     
Building and Land Improvements 34,731,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7740MilestoneParkwayMember
     
Total 38,556,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7740MilestoneParkwayMember
[2],[3]      
Accumulated Depreciation (4,003,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7740MilestoneParkwayMember
[4]      
7770 Backlick Road        
Initial Cost        
Land 6,387,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7770BacklickRoadMember
     
Building and Land Improvements 74,325,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7770BacklickRoadMember
     
Costs Capitalized Subsequent to Acquisition 140,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7770BacklickRoadMember
     
Gross Amounts Carried at Close of Period        
Land 6,387,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7770BacklickRoadMember
     
Building and Land Improvements 74,465,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7770BacklickRoadMember
     
Total 80,852,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7770BacklickRoadMember
[2],[3]      
Accumulated Depreciation (3,414,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7770BacklickRoadMember
[4]      
7880 Milestone Parkway        
Initial Cost        
Land 4,857,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7880MilestoneParkwayMember
[5]      
Building and Land Improvements 12,221,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7880MilestoneParkwayMember
[5]      
Costs Capitalized Subsequent to Acquisition 0us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7880MilestoneParkwayMember
[5]      
Gross Amounts Carried at Close of Period        
Land 4,857,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7880MilestoneParkwayMember
[5]      
Building and Land Improvements 12,221,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7880MilestoneParkwayMember
[5]      
Total 17,078,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7880MilestoneParkwayMember
[2],[3],[5]      
Accumulated Depreciation 0us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number7880MilestoneParkwayMember
[4],[5]      
8003 Corporate Drive        
Initial Cost        
Land 611,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8003CorporateDriveMember
     
Building and Land Improvements 1,611,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8003CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 655,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8003CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 611,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8003CorporateDriveMember
     
Building and Land Improvements 2,266,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8003CorporateDriveMember
     
Total 2,877,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8003CorporateDriveMember
[2],[3]      
Accumulated Depreciation (396,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8003CorporateDriveMember
[4]      
8007 Corporate Drive        
Initial Cost        
Land 1,434,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8007CorporateDriveMember
     
Building and Land Improvements 3,336,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8007CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,034,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8007CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,434,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8007CorporateDriveMember
     
Building and Land Improvements 4,370,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8007CorporateDriveMember
     
Total 5,804,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8007CorporateDriveMember
[2],[3]      
Accumulated Depreciation (938,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8007CorporateDriveMember
[4]      
8010 Corporate Drive        
Initial Cost        
Land 1,349,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8010CorporateDriveMember
     
Building and Land Improvements 3,262,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8010CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,744,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8010CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,349,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8010CorporateDriveMember
     
Building and Land Improvements 5,006,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8010CorporateDriveMember
     
Total 6,355,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8010CorporateDriveMember
[2],[3]      
Accumulated Depreciation (1,282,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8010CorporateDriveMember
[4]      
8013 Corporate Drive        
Initial Cost        
Land 642,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8013CorporateDriveMember
     
Building and Land Improvements 1,536,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8013CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,809,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8013CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 642,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8013CorporateDriveMember
     
Building and Land Improvements 3,345,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8013CorporateDriveMember
     
Total 3,987,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8013CorporateDriveMember
[2],[3]      
Accumulated Depreciation (770,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8013CorporateDriveMember
[4]      
8015 Corporate Drive        
Initial Cost        
Land 446,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8015CorporateDriveMember
     
Building and Land Improvements 1,116,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8015CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 361,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8015CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 446,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8015CorporateDriveMember
     
Building and Land Improvements 1,477,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8015CorporateDriveMember
     
Total 1,923,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8015CorporateDriveMember
[2],[3]      
Accumulated Depreciation (428,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8015CorporateDriveMember
[4]      
8019 Corporate Drive        
Initial Cost        
Land 680,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8019CorporateDriveMember
     
Building and Land Improvements 1,898,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8019CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 739,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8019CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 680,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8019CorporateDriveMember
     
Building and Land Improvements 2,637,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8019CorporateDriveMember
     
Total 3,317,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8019CorporateDriveMember
[2],[3]      
Accumulated Depreciation (751,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8019CorporateDriveMember
[4]      
8020 Corporate Drive        
Initial Cost        
Land 2,184,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8020CorporateDriveMember
     
Building and Land Improvements 3,767,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8020CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,205,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8020CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,184,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8020CorporateDriveMember
     
Building and Land Improvements 5,972,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8020CorporateDriveMember
     
Total 8,156,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8020CorporateDriveMember
[2],[3]      
Accumulated Depreciation (1,499,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8020CorporateDriveMember
[4]      
8023 Corporate Drive        
Initial Cost        
Land 651,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8023CorporateDriveMember
     
Building and Land Improvements 1,603,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8023CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 5,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8023CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 651,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8023CorporateDriveMember
     
Building and Land Improvements 1,608,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8023CorporateDriveMember
     
Total 2,259,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8023CorporateDriveMember
[2],[3]      
Accumulated Depreciation (357,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8023CorporateDriveMember
[4]      
8094 Sandpiper Circle        
Initial Cost        
Land 1,960,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8094SandpiperCircleMember
     
Building and Land Improvements 3,716,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8094SandpiperCircleMember
     
Costs Capitalized Subsequent to Acquisition 941,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8094SandpiperCircleMember
     
Gross Amounts Carried at Close of Period        
Land 1,960,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8094SandpiperCircleMember
     
Building and Land Improvements 4,657,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8094SandpiperCircleMember
     
Total 6,617,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8094SandpiperCircleMember
[2],[3]      
Accumulated Depreciation (1,125,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8094SandpiperCircleMember
[4]      
8098 Sandpiper Circle        
Initial Cost        
Land 1,797,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8098SandpiperCircleMember
     
Building and Land Improvements 3,651,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8098SandpiperCircleMember
     
Costs Capitalized Subsequent to Acquisition 639,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8098SandpiperCircleMember
     
Gross Amounts Carried at Close of Period        
Land 1,797,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8098SandpiperCircleMember
     
Building and Land Improvements 4,290,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8098SandpiperCircleMember
     
Total 6,087,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8098SandpiperCircleMember
[2],[3]      
Accumulated Depreciation (827,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8098SandpiperCircleMember
[4]      
8110 Corporate Drive        
Initial Cost        
Land 2,285,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8110CorporateDriveMember
     
Building and Land Improvements 10,117,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8110CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 989,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8110CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,285,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8110CorporateDriveMember
     
Building and Land Improvements 11,106,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8110CorporateDriveMember
     
Total 13,391,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8110CorporateDriveMember
[2],[3]      
Accumulated Depreciation (2,870,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8110CorporateDriveMember
[4]      
8140 Corporate Drive        
Initial Cost        
Land 2,158,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8140CorporateDriveMember
     
Building and Land Improvements 8,457,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8140CorporateDriveMember
     
Costs Capitalized Subsequent to Acquisition 3,008,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8140CorporateDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,158,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8140CorporateDriveMember
     
Building and Land Improvements 11,465,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8140CorporateDriveMember
     
Total 13,623,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8140CorporateDriveMember
[2],[3]      
Accumulated Depreciation (3,767,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8140CorporateDriveMember
[4]      
8621 Robert Fulton Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8621RobertFultonDriveMember
[1]      
Initial Cost        
Land 2,317,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8621RobertFultonDriveMember
     
Building and Land Improvements 12,642,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8621RobertFultonDriveMember
     
Costs Capitalized Subsequent to Acquisition 336,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8621RobertFultonDriveMember
     
Gross Amounts Carried at Close of Period        
Land 2,317,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8621RobertFultonDriveMember
     
Building and Land Improvements 12,978,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8621RobertFultonDriveMember
     
Total 15,295,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8621RobertFultonDriveMember
[2],[3]      
Accumulated Depreciation (3,015,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8621RobertFultonDriveMember
[4]      
8661 Robert Fulton Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8661RobertFultonDriveMember
[1]      
Initial Cost        
Land 1,510,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8661RobertFultonDriveMember
     
Building and Land Improvements 3,764,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8661RobertFultonDriveMember
     
Costs Capitalized Subsequent to Acquisition 2,423,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8661RobertFultonDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,510,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8661RobertFultonDriveMember
     
Building and Land Improvements 6,187,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8661RobertFultonDriveMember
     
Total 7,697,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8661RobertFultonDriveMember
[2],[3]      
Accumulated Depreciation (1,848,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8661RobertFultonDriveMember
[4]      
8671 Robert Fulton Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8671RobertFultonDriveMember
[1]      
Initial Cost        
Land 1,718,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8671RobertFultonDriveMember
     
Building and Land Improvements 4,280,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8671RobertFultonDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,981,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8671RobertFultonDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,718,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8671RobertFultonDriveMember
     
Building and Land Improvements 6,261,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8671RobertFultonDriveMember
     
Total 7,979,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8671RobertFultonDriveMember
[2],[3]      
Accumulated Depreciation (2,754,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number8671RobertFultonDriveMember
[4]      
870 Elkridge Landing Road        
Real Estate and Accumulated Depreciation        
Encumbrances 0us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number870ElkridgeLandingRoadMember
[1]      
Initial Cost        
Land 2,003,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number870ElkridgeLandingRoadMember
     
Building and Land Improvements 9,442,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number870ElkridgeLandingRoadMember
     
Costs Capitalized Subsequent to Acquisition 6,941,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number870ElkridgeLandingRoadMember
     
Gross Amounts Carried at Close of Period        
Land 2,003,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number870ElkridgeLandingRoadMember
     
Building and Land Improvements 16,383,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number870ElkridgeLandingRoadMember
     
Total 18,386,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number870ElkridgeLandingRoadMember
[2],[3]      
Accumulated Depreciation (7,965,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number870ElkridgeLandingRoadMember
[4]      
891 Elkridge Landing Road        
Initial Cost        
Land 1,165,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number891ElkridgeLandingRoadMember
     
Building and Land Improvements 4,772,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number891ElkridgeLandingRoadMember
     
Costs Capitalized Subsequent to Acquisition 2,295,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number891ElkridgeLandingRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,165,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number891ElkridgeLandingRoadMember
     
Building and Land Improvements 7,067,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number891ElkridgeLandingRoadMember
     
Total 8,232,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number891ElkridgeLandingRoadMember
[2],[3]      
Accumulated Depreciation (3,229,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number891ElkridgeLandingRoadMember
[4]      
900 Elkridge Landing Road        
Initial Cost        
Land 1,993,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number900ElkridgeLandingRoadMember
     
Building and Land Improvements 7,972,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number900ElkridgeLandingRoadMember
     
Costs Capitalized Subsequent to Acquisition 3,486,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number900ElkridgeLandingRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,993,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number900ElkridgeLandingRoadMember
     
Building and Land Improvements 11,458,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number900ElkridgeLandingRoadMember
     
Total 13,451,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number900ElkridgeLandingRoadMember
[2],[3]      
Accumulated Depreciation (5,655,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number900ElkridgeLandingRoadMember
[4]      
901 Elkridge Landing Road        
Initial Cost        
Land 1,156,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number901ElkridgeLandingRoadMember
     
Building and Land Improvements 4,437,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number901ElkridgeLandingRoadMember
     
Costs Capitalized Subsequent to Acquisition 2,419,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number901ElkridgeLandingRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,156,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number901ElkridgeLandingRoadMember
     
Building and Land Improvements 6,856,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number901ElkridgeLandingRoadMember
     
Total 8,012,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number901ElkridgeLandingRoadMember
[2],[3]      
Accumulated Depreciation (2,672,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number901ElkridgeLandingRoadMember
[4]      
911 Elkridge Landing Road        
Initial Cost        
Land 1,215,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number911ElkridgeLandingRoadMember
     
Building and Land Improvements 4,861,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number911ElkridgeLandingRoadMember
     
Costs Capitalized Subsequent to Acquisition 2,024,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number911ElkridgeLandingRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,215,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number911ElkridgeLandingRoadMember
     
Building and Land Improvements 6,885,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number911ElkridgeLandingRoadMember
     
Total 8,100,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number911ElkridgeLandingRoadMember
[2],[3]      
Accumulated Depreciation (3,239,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number911ElkridgeLandingRoadMember
[4]      
921 Elkridge Landing Road        
Initial Cost        
Land 1,044,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number921ElkridgeLandingRoadMember
[5]      
Building and Land Improvements 4,239,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number921ElkridgeLandingRoadMember
[5]      
Costs Capitalized Subsequent to Acquisition 748,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number921ElkridgeLandingRoadMember
[5]      
Gross Amounts Carried at Close of Period        
Land 1,044,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number921ElkridgeLandingRoadMember
[5]      
Building and Land Improvements 4,987,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number921ElkridgeLandingRoadMember
[5]      
Total 6,031,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number921ElkridgeLandingRoadMember
[2],[3],[5]      
Accumulated Depreciation (2,244,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number921ElkridgeLandingRoadMember
[4],[5]      
938 Elkridge Landing Road        
Initial Cost        
Land 1,163,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number938ElkridgeLandingRoadMember
     
Building and Land Improvements 4,748,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number938ElkridgeLandingRoadMember
     
Costs Capitalized Subsequent to Acquisition 1,155,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number938ElkridgeLandingRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,163,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number938ElkridgeLandingRoadMember
     
Building and Land Improvements 5,903,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number938ElkridgeLandingRoadMember
     
Total 7,066,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number938ElkridgeLandingRoadMember
[2],[3]      
Accumulated Depreciation (1,928,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number938ElkridgeLandingRoadMember
[4]      
939 Elkridge Landing Road        
Initial Cost        
Land 939,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number939ElkridgeLandingRoadMember
     
Building and Land Improvements 3,756,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number939ElkridgeLandingRoadMember
     
Costs Capitalized Subsequent to Acquisition 3,074,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number939ElkridgeLandingRoadMember
     
Gross Amounts Carried at Close of Period        
Land 939,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number939ElkridgeLandingRoadMember
     
Building and Land Improvements 6,830,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number939ElkridgeLandingRoadMember
     
Total 7,769,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number939ElkridgeLandingRoadMember
[2],[3]      
Accumulated Depreciation (2,927,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number939ElkridgeLandingRoadMember
[4]      
940 Elkridge Landing Road        
Initial Cost        
Land 1,104,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number940ElkridgeLandingRoadMember
[6]      
Building and Land Improvements 4,730,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number940ElkridgeLandingRoadMember
[6]      
Costs Capitalized Subsequent to Acquisition 170,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number940ElkridgeLandingRoadMember
[6]      
Gross Amounts Carried at Close of Period        
Land 1,104,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number940ElkridgeLandingRoadMember
[6]      
Building and Land Improvements 4,900,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number940ElkridgeLandingRoadMember
[6]      
Total 6,004,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number940ElkridgeLandingRoadMember
[2],[3],[6]      
Accumulated Depreciation (4,884,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number940ElkridgeLandingRoadMember
[4],[6]      
9651 Hornbaker Road        
Initial Cost        
Land 6,050,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9651HornbakerRoadMember
     
Building and Land Improvements 204,176,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9651HornbakerRoadMember
     
Costs Capitalized Subsequent to Acquisition 853,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9651HornbakerRoadMember
     
Gross Amounts Carried at Close of Period        
Land 6,050,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9651HornbakerRoadMember
     
Building and Land Improvements 205,029,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9651HornbakerRoadMember
     
Total 211,079,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9651HornbakerRoadMember
[2],[3]      
Accumulated Depreciation (10,881,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9651HornbakerRoadMember
[4]      
9690 Deereco Road        
Initial Cost        
Land 3,415,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9690DeerecoRoadMember
     
Building and Land Improvements 13,723,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9690DeerecoRoadMember
     
Costs Capitalized Subsequent to Acquisition 7,289,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9690DeerecoRoadMember
     
Gross Amounts Carried at Close of Period        
Land 3,415,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9690DeerecoRoadMember
     
Building and Land Improvements 21,012,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9690DeerecoRoadMember
     
Total 24,427,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9690DeerecoRoadMember
[2],[3]      
Accumulated Depreciation (9,585,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9690DeerecoRoadMember
[4]      
9900 Franklin Square Drive        
Initial Cost        
Land 979,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9900FranklinSquareDriveMember
     
Building and Land Improvements 3,466,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9900FranklinSquareDriveMember
     
Costs Capitalized Subsequent to Acquisition 325,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9900FranklinSquareDriveMember
     
Gross Amounts Carried at Close of Period        
Land 979,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9900FranklinSquareDriveMember
     
Building and Land Improvements 3,791,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9900FranklinSquareDriveMember
     
Total 4,770,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9900FranklinSquareDriveMember
[2],[3]      
Accumulated Depreciation (989,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9900FranklinSquareDriveMember
[4]      
9910 Franklin Square Drive        
Real Estate and Accumulated Depreciation        
Encumbrances 4,691,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9910FranklinSquareDriveMember
[1]      
Initial Cost        
Land 1,219,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9910FranklinSquareDriveMember
     
Building and Land Improvements 6,590,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9910FranklinSquareDriveMember
     
Costs Capitalized Subsequent to Acquisition 74,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9910FranklinSquareDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,219,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9910FranklinSquareDriveMember
     
Building and Land Improvements 6,664,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9910FranklinSquareDriveMember
     
Total 7,883,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9910FranklinSquareDriveMember
[2],[3]      
Accumulated Depreciation (1,952,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9910FranklinSquareDriveMember
[4]      
9920 Franklin Square Drive        
Initial Cost        
Land 1,058,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9920FranklinSquareDriveMember
     
Building and Land Improvements 5,293,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9920FranklinSquareDriveMember
     
Costs Capitalized Subsequent to Acquisition 1,436,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9920FranklinSquareDriveMember
     
Gross Amounts Carried at Close of Period        
Land 1,058,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9920FranklinSquareDriveMember
     
Building and Land Improvements 6,729,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9920FranklinSquareDriveMember
     
Total 7,787,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9920FranklinSquareDriveMember
[2],[3]      
Accumulated Depreciation (2,077,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Number9920FranklinSquareDriveMember
[4]      
Aerotech Commerce        
Initial Cost        
Land 900,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_AerotechCommerceMember
[6]      
Gross Amounts Carried at Close of Period        
Land 900,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_AerotechCommerceMember
[6]      
Total 900,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_AerotechCommerceMember
[2],[3],[6]      
Arborcrest        
Initial Cost        
Land 21,968,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArborcrestMember
[5]      
Building and Land Improvements 109,468,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArborcrestMember
[5]      
Costs Capitalized Subsequent to Acquisition 1,209,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArborcrestMember
[5]      
Gross Amounts Carried at Close of Period        
Land 21,968,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArborcrestMember
[5]      
Building and Land Improvements 110,677,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArborcrestMember
[5]      
Total 132,645,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArborcrestMember
[2],[3],[5]      
Accumulated Depreciation (22,043,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArborcrestMember
[4],[5]      
Arundel Preserve        
Initial Cost        
Land 13,401,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArundelPreserveMember
[6]      
Building and Land Improvements 7,238,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArundelPreserveMember
[6]      
Gross Amounts Carried at Close of Period        
Land 13,401,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArundelPreserveMember
[6]      
Building and Land Improvements 7,238,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArundelPreserveMember
[6]      
Total 20,639,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ArundelPreserveMember
[2],[3],[6]      
Ashburn Crossing - DC 10        
Initial Cost        
Land 4,408,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_AshburnCrossingDC10Member
[5]      
Building and Land Improvements 8,399,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_AshburnCrossingDC10Member
[5]      
Gross Amounts Carried at Close of Period        
Land 4,408,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_AshburnCrossingDC10Member
[5]      
Building and Land Improvements 8,399,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_AshburnCrossingDC10Member
[5]      
Total 12,807,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_AshburnCrossingDC10Member
[2],[3],[5]      
Accumulated Depreciation 0us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_AshburnCrossingDC10Member
[4],[5]      
Canton Crossing Land        
Initial Cost        
Land 16,085,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingLandMember
[6]      
Building and Land Improvements 905,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingLandMember
[6]      
Gross Amounts Carried at Close of Period        
Land 16,085,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingLandMember
[6]      
Building and Land Improvements 905,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingLandMember
[6]      
Total 16,990,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingLandMember
[2],[3],[6]      
Canton Crossing Util Distr Ctr        
Initial Cost        
Land 7,300,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingUtilDistrCtrMember
     
Building and Land Improvements 15,556,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingUtilDistrCtrMember
     
Costs Capitalized Subsequent to Acquisition 878,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingUtilDistrCtrMember
     
Gross Amounts Carried at Close of Period        
Land 7,300,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingUtilDistrCtrMember
     
Building and Land Improvements 16,434,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingUtilDistrCtrMember
     
Total 23,734,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingUtilDistrCtrMember
[2],[3]      
Accumulated Depreciation (2,755,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_CantonCrossingUtilDistrCtrMember
[4]      
Columbia Gateway - Southridge        
Initial Cost        
Land 6,387,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ColumbiaGatewayParcelTTo11Member
[6]      
Building and Land Improvements 2,940,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ColumbiaGatewayParcelTTo11Member
[6]      
Gross Amounts Carried at Close of Period        
Land 6,387,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ColumbiaGatewayParcelTTo11Member
[6]      
Building and Land Improvements 2,940,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ColumbiaGatewayParcelTTo11Member
[6]      
Total 9,327,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ColumbiaGatewayParcelTTo11Member
[2],[3],[6]      
Dahlgren Technology Center        
Initial Cost        
Land 978,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_DahlgrenTechnologyCenterMember
[6]      
Building and Land Improvements 178,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_DahlgrenTechnologyCenterMember
[6]      
Gross Amounts Carried at Close of Period        
Land 978,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_DahlgrenTechnologyCenterMember
[6]      
Building and Land Improvements 178,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_DahlgrenTechnologyCenterMember
[6]      
Total 1,156,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_DahlgrenTechnologyCenterMember
[2],[3],[6]      
Expedition VII        
Initial Cost        
Land 705,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ExpeditionViiMember
[6]      
Building and Land Improvements 727,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ExpeditionViiMember
[6]      
Gross Amounts Carried at Close of Period        
Land 705,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ExpeditionViiMember
[6]      
Building and Land Improvements 727,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ExpeditionViiMember
[6]      
Total 1,432,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_ExpeditionViiMember
[2],[3],[6]      
InterQuest        
Initial Cost        
Land 14,382,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_InterQuestMember
[6]      
Building and Land Improvements 9,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_InterQuestMember
[6]      
Gross Amounts Carried at Close of Period        
Land 14,382,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_InterQuestMember
[6]      
Building and Land Improvements 9,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_InterQuestMember
[6]      
Total 14,391,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_InterQuestMember
[2],[3],[6]      
M Square Research Park        
Initial Cost        
Building and Land Improvements 3,129,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_MSquareResearchParkMember
[6]      
Gross Amounts Carried at Close of Period        
Building and Land Improvements 3,129,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_MSquareResearchParkMember
[6]      
Total 3,129,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_MSquareResearchParkMember
[2],[3],[6]      
National Business Park North        
Initial Cost        
Land 27,785,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NationalBusinessParkNorthMember
[6]      
Building and Land Improvements 47,411,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NationalBusinessParkNorthMember
[6]      
Gross Amounts Carried at Close of Period        
Land 27,785,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NationalBusinessParkNorthMember
[6]      
Building and Land Improvements 47,411,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NationalBusinessParkNorthMember
[6]      
Total 75,196,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NationalBusinessParkNorthMember
[2],[3],[6]      
North Gate Business Park        
Initial Cost        
Land 6,486,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthGateBusinessParkMember
[6]      
Building and Land Improvements 10,922,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthGateBusinessParkMember
[6]      
Gross Amounts Carried at Close of Period        
Land 6,486,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthGateBusinessParkMember
[6]      
Building and Land Improvements 10,922,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthGateBusinessParkMember
[6]      
Total 17,408,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthGateBusinessParkMember
[2],[3],[6]      
Northwest Crossroads        
Initial Cost        
Land 7,430,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthwestCrossroadsMember
[6]      
Building and Land Improvements 836,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthwestCrossroadsMember
[6]      
Gross Amounts Carried at Close of Period        
Land 7,430,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthwestCrossroadsMember
[6]      
Building and Land Improvements 836,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthwestCrossroadsMember
[6]      
Total 8,266,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NorthwestCrossroadsMember
[2],[3],[6]      
NOVA Office A        
Initial Cost        
Land 2,096,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeAMember
[5],[7]      
Building and Land Improvements 38,142,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeAMember
[5],[7]      
Gross Amounts Carried at Close of Period        
Land 2,096,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeAMember
[5],[7]      
Building and Land Improvements 38,142,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeAMember
[5],[7]      
Total 40,238,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeAMember
[2],[3],[5],[7]      
NOVA Office B        
Initial Cost        
Land 739,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeBMember
[5],[7]      
Building and Land Improvements 18,858,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeBMember
[5],[7]      
Gross Amounts Carried at Close of Period        
Land 739,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeBMember
[5],[7]      
Building and Land Improvements 18,858,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeBMember
[5],[7]      
Total 19,597,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeBMember
[2],[3],[5],[7]      
NOVA Office D        
Initial Cost        
Land 6,587,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeDMember
[5]      
Building and Land Improvements 2,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeDMember
[5]      
Gross Amounts Carried at Close of Period        
Land 6,587,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeDMember
[5]      
Building and Land Improvements 2,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeDMember
[5]      
Total 6,589,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_NOVAOfficeDMember
[2],[3],[5]      
Old Annapolis Road        
Initial Cost        
Land 1,637,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OldAnnapolisRoadMember
     
Building and Land Improvements 5,500,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OldAnnapolisRoadMember
     
Costs Capitalized Subsequent to Acquisition 2,421,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OldAnnapolisRoadMember
     
Gross Amounts Carried at Close of Period        
Land 1,637,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OldAnnapolisRoadMember
     
Building and Land Improvements 7,921,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OldAnnapolisRoadMember
     
Total 9,558,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OldAnnapolisRoadMember
[2],[3]      
Accumulated Depreciation (2,756,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OldAnnapolisRoadMember
[4]      
Patriot Park        
Initial Cost        
Land 8,723,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotParkMember
[6]      
Building and Land Improvements 248,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotParkMember
[6]      
Gross Amounts Carried at Close of Period        
Land 8,723,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotParkMember
[6]      
Building and Land Improvements 248,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotParkMember
[6]      
Total 8,971,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotParkMember
[2],[3],[6]      
Patriot Ridge        
Initial Cost        
Land 18,517,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotRidgeMember
[6]      
Building and Land Improvements 14,440,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotRidgeMember
[6]      
Gross Amounts Carried at Close of Period        
Land 18,517,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotRidgeMember
[6]      
Building and Land Improvements 14,440,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotRidgeMember
[6]      
Total 32,957,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_PatriotRidgeMember
[2],[3],[6]      
Redstone Gateway        
Initial Cost        
Building and Land Improvements 14,087,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_RedstoneGatewayMember
[6]      
Gross Amounts Carried at Close of Period        
Building and Land Improvements 14,087,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_RedstoneGatewayMember
[6]      
Total 14,087,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_RedstoneGatewayMember
[2],[3],[6]      
Route 15/Biggs Ford Road        
Initial Cost        
Land 8,703,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Route15BiggsFordRoadMember
[6]      
Building and Land Improvements 541,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Route15BiggsFordRoadMember
[6]      
Gross Amounts Carried at Close of Period        
Land 8,703,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Route15BiggsFordRoadMember
[6]      
Building and Land Improvements 541,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Route15BiggsFordRoadMember
[6]      
Total 9,244,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_Route15BiggsFordRoadMember
[2],[3],[6]      
Sentry Gateway        
Initial Cost        
Land 8,275,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayMember
[6]      
Building and Land Improvements 3,645,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayMember
[6]      
Gross Amounts Carried at Close of Period        
Land 8,275,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayMember
[6]      
Building and Land Improvements 3,645,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayMember
[6]      
Total 11,920,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayMember
[2],[3],[6]      
Sentry Gateway - T        
Initial Cost        
Land 14,020,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayTMember
     
Building and Land Improvements 38,804,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayTMember
     
Costs Capitalized Subsequent to Acquisition 13,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayTMember
     
Gross Amounts Carried at Close of Period        
Land 14,020,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayTMember
     
Building and Land Improvements 38,817,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayTMember
     
Total 52,837,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayTMember
[2],[3]      
Accumulated Depreciation (7,646,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayTMember
[4]      
Sentry Gateway - V        
Initial Cost        
Building and Land Improvements 1,066,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayVMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 1,066,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayVMember
     
Total 1,066,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayVMember
[2],[3]      
Accumulated Depreciation (161,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayVMember
[4]      
Sentry Gateway - W        
Initial Cost        
Building and Land Improvements 1,884,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayWMember
     
Gross Amounts Carried at Close of Period        
Building and Land Improvements 1,884,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayWMember
     
Total 1,884,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayWMember
[2],[3]      
Accumulated Depreciation (249,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayWMember
[4]      
Sentry Gateway - X        
Initial Cost        
Land 1,964,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayXMember
     
Building and Land Improvements 21,178,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayXMember
     
Gross Amounts Carried at Close of Period        
Land 1,964,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayXMember
     
Building and Land Improvements 21,178,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayXMember
     
Total 23,142,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayXMember
[2],[3]      
Accumulated Depreciation (2,204,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayXMember
[4]      
Sentry Gateway - Y        
Initial Cost        
Land 1,964,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayYMember
     
Building and Land Improvements 21,298,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayYMember
     
Gross Amounts Carried at Close of Period        
Land 1,964,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayYMember
     
Building and Land Improvements 21,298,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayYMember
     
Total 23,262,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayYMember
[2],[3]      
Accumulated Depreciation (2,213,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayYMember
[4]      
Sentry Gateway - Z        
Initial Cost        
Land 1,964,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayZMember
[5]      
Building and Land Improvements 23,185,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayZMember
[5]      
Gross Amounts Carried at Close of Period        
Land 1,964,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayZMember
[5]      
Building and Land Improvements 23,185,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayZMember
[5]      
Total 25,149,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_SentryGatewayZMember
[2],[3],[5]      
Westfields - Park Center        
Initial Cost        
Land 16,418,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsParkCenterMember
[6]      
Building and Land Improvements 8,584,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsParkCenterMember
[6]      
Gross Amounts Carried at Close of Period        
Land 16,418,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsParkCenterMember
[6]      
Building and Land Improvements 8,584,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsParkCenterMember
[6]      
Total 25,002,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsParkCenterMember
[2],[3],[6]      
Westfields Corporate Center        
Initial Cost        
Land 7,141,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsCorporateCenterMember
[6]      
Building and Land Improvements 1,415,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsCorporateCenterMember
[6]      
Gross Amounts Carried at Close of Period        
Land 7,141,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsCorporateCenterMember
[6]      
Building and Land Improvements 1,415,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsCorporateCenterMember
[6]      
Total 8,556,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WestfieldsCorporateCenterMember
[2],[3],[6]      
White Marsh        
Initial Cost        
Land 17,610,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WhiteMarshMember
[6]      
Building and Land Improvements 6,983,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WhiteMarshMember
[6]      
Gross Amounts Carried at Close of Period        
Land 17,610,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WhiteMarshMember
[6]      
Building and Land Improvements 6,983,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WhiteMarshMember
[6]      
Total 24,593,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WhiteMarshMember
[2],[3],[6]      
Woodland Park        
Initial Cost        
Land 9,614,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WoodlandParkMember
[6]      
Building and Land Improvements 81,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WoodlandParkMember
[6]      
Gross Amounts Carried at Close of Period        
Land 9,614,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WoodlandParkMember
[6]      
Building and Land Improvements 81,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WoodlandParkMember
[6]      
Total 9,695,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_WoodlandParkMember
[2],[3],[6]      
Other Developments, including intercompany eliminations        
Initial Cost        
Land 8,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OtherDevelopmentsIncludingIntercompanyEliminationsMember
     
Building and Land Improvements 276,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OtherDevelopmentsIncludingIntercompanyEliminationsMember
     
Costs Capitalized Subsequent to Acquisition 261,000us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OtherDevelopmentsIncludingIntercompanyEliminationsMember
     
Gross Amounts Carried at Close of Period        
Land 8,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OtherDevelopmentsIncludingIntercompanyEliminationsMember
     
Building and Land Improvements 537,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OtherDevelopmentsIncludingIntercompanyEliminationsMember
     
Total 545,000us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OtherDevelopmentsIncludingIntercompanyEliminationsMember
[2],[3]      
Accumulated Depreciation (26,000)us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= ofc_OtherDevelopmentsIncludingIntercompanyEliminationsMember
[4]      
Other Properties with Shortened Holding Periods | Fair value measurement on a nonrecurring basis | Greater Baltimore        
Additional information        
Impairment losses $ 1,371,000us-gaap_AssetImpairmentCharges
/ ofc_AssetsbyTypeAxis
= ofc_OtherPropertieswithShortenedHoldingPeriodsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsNonrecurringMember
/ invest_InvestmentGeographicRegionAxis
= ofc_GreaterBaltimoreMember
$ 5,900,000us-gaap_AssetImpairmentCharges
/ ofc_AssetsbyTypeAxis
= ofc_OtherPropertieswithShortenedHoldingPeriodsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsNonrecurringMember
/ invest_InvestmentGeographicRegionAxis
= ofc_GreaterBaltimoreMember
   
[1] Excludes our Revolving Credit Facility of $83.0 million, term loan facilities of $520.0 million, unsecured senior notes of $890.9 million, exchangeable senior notes of $572,000, unsecured notes payable of $1.6 million, a letter of credit on a mortgage loan of $14.8 million, and net premiums on the remaining loans of $42,000.
[2] As discussed in Note 3 to our Consolidated Financial Statements, we recognized impairment losses of $1.4 million primarily in connection with certain of our operating properties in the Greater Baltimore region that were disposed in the current period.
[3] The aggregate cost of these assets for Federal income tax purposes was approximately $3.4 billion at December 31, 2014.
[4] The estimated lives over which depreciation is recognized follow: Building and land improvements: 10-40 years; and tenant improvements: related lease terms.
[5] Under construction or redevelopment at December 31, 2014.
[6] Held or under pre-construction at December 31, 2014.
[7] The carrying amounts of these properties under construction exclude allocated costs of the garage being constructed to support the properties.