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.