Annual report pursuant to Section 13 and 15(d)

Debt (Details)

v2.4.1.9
Debt (Details) (USD $)
 12 Months Ended 1 Months Ended 0 Months Ended 12 Months Ended 0 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2014
Sep. 01, 2011
Feb. 14, 2012
Aug. 03, 2012
Dec. 31, 2010
May 06, 2013
Sep. 16, 2013
May 14, 2014
Apr. 30, 2014
Debt                        
Debt, net $ 1,920,057,000us-gaap_LongTermDebt $ 1,927,703,000us-gaap_LongTermDebt   $ 1,920,057,000us-gaap_LongTermDebt                
Loss on early extinguishment of debt 9,552,000us-gaap_GainsLossesOnExtinguishmentOfDebt 27,030,000us-gaap_GainsLossesOnExtinguishmentOfDebt 943,000us-gaap_GainsLossesOnExtinguishmentOfDebt                  
Principal amount of debt 1,929,810,000us-gaap_DebtInstrumentCarryingAmount [1]     1,929,810,000us-gaap_DebtInstrumentCarryingAmount [1]                
Interest expense associated with amortization of discount 921,000us-gaap_AmortizationOfDebtDiscountPremium 1,159,000us-gaap_AmortizationOfDebtDiscountPremium 3,155,000us-gaap_AmortizationOfDebtDiscountPremium                  
Secured Loans Due November 2015 and January 2016                        
Debt                        
Loss on early extinguishment of debt       9,100,000us-gaap_GainsLossesOnExtinguishmentOfDebt
/ us-gaap_ExtinguishmentOfDebtAxis
= ofc_SecuredLoansDueNovember2015AndJanuary2016Member 		               
Secured Loan Due January 2016                        
Debt                        
Stated interest rate (as a percent) 5.56%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_ExtinguishmentOfDebtAxis
= ofc_SecuredLoanDueJanuary2016Member 		    5.56%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_ExtinguishmentOfDebtAxis
= ofc_SecuredLoanDueJanuary2016Member 		               
Amount of loans repaid upon entry into Revolving Credit Facility and Term Loan Agreement       108,500,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_ExtinguishmentOfDebtAxis
= ofc_SecuredLoanDueJanuary2016Member 		               
Secured Loan Due November 2015                        
Debt                        
Stated interest rate (as a percent) 5.53%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_ExtinguishmentOfDebtAxis
= ofc_SecuredLoanDueNovember2015Member 		    5.53%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_ExtinguishmentOfDebtAxis
= ofc_SecuredLoanDueNovember2015Member 		               
Amount of loans repaid upon entry into Revolving Credit Facility and Term Loan Agreement       103,000,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_ExtinguishmentOfDebtAxis
= ofc_SecuredLoanDueNovember2015Member 		               
Mortgage and Other Secured Loans:                        
Debt                        
Debt, net 424,016,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_SecuredDebtMember 		712,751,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_SecuredDebtMember 		  424,016,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_SecuredDebtMember 		               
Fixed rate mortgage loans                        
Debt                        
Debt, net 387,139,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		675,060,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		  387,139,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		               
Stated Interest Rates, low end of range (as a percent) 3.96%us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		[2]                      
Stated Interest Rates, high end of range (as a percent) 10.65%us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		[2]                      
Unamortized premium included in carrying value 42,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		69,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		  42,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		               
Weighted average interest rate (as a percent) 8.10%us-gaap_DebtWeightedAverageInterestRate
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		    8.10%us-gaap_DebtWeightedAverageInterestRate
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		               
Weighted average interest rate excluding incremental rate 6.16%ofc_DebtWeightedAverageInterestRateExcludingIncrementalRateOnDefaultRate
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		    6.16%ofc_DebtWeightedAverageInterestRateExcludingIncrementalRateOnDefaultRate
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember 		               
Variable rate secured loans                        
Debt                        
Debt, net 36,877,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_VariableRateSecuredDebtMember 		37,691,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_VariableRateSecuredDebtMember 		  36,877,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_VariableRateSecuredDebtMember 		               
Stated interest rate (as a percent) 2.41%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_VariableRateSecuredDebtMember 		    2.41%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_VariableRateSecuredDebtMember 		               
Description of variable rate basis LIBOR [3]                      
Variable rate, spread (as a percent) 2.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_VariableRateSecuredDebtMember 		[3]                      
Revolving Credit Facility                        
Debt                        
Debt, net 83,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		0us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		  83,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		               
Description of variable rate basis LIBOR                      
Term Credit Facility Effective September 2011                        
Debt                        
Additional borrowing capacity available provided there is no default under the agreement         100,000,000ofc_CreditFacilityAdditionalBorrowingCapacityAvailable
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveSeptember2011Member 		             
Extension option period (in years)         1 year              
Initial amount borrowed         400,000,000us-gaap_ProceedsFromIssuanceOfDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveSeptember2011Member 		             
Extension fee as a percentage of total availability of the facility         0.15%ofc_CreditFacilityExtensionFeePercentageOfTotalAvailabilityOfFacility
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveSeptember2011Member 		             
Repayments of Debt 100,000,000us-gaap_RepaymentsOfDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveSeptember2011Member 		150,000,000us-gaap_RepaymentsOfDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveSeptember2011Member 		                   
Term Credit Facility Effective February 2012                        
Debt                        
Extension option period (in years)           1 year            
Initial amount borrowed           250,000,000us-gaap_ProceedsFromIssuanceOfDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveFebruary2012Member 		           
Extension fee as a percentage of total availability of the facility           0.15%ofc_CreditFacilityExtensionFeePercentageOfTotalAvailabilityOfFacility
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveFebruary2012Member 		           
Term Credit Facility Effective August 2012                        
Debt                        
Additional borrowing capacity available provided there is no default under the agreement             80,000,000ofc_CreditFacilityAdditionalBorrowingCapacityAvailable
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveAugust2012Member 		         
Initial amount borrowed             120,000,000us-gaap_ProceedsFromIssuanceOfDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveAugust2012Member 		         
Term Loan Facilities                        
Debt                        
Debt, net 520,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember 		620,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember 		  520,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember 		               
Description of variable rate basis LIBOR [4]                      
Weighted average interest rate (as a percent) 1.80%us-gaap_DebtWeightedAverageInterestRate
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember 		    1.80%us-gaap_DebtWeightedAverageInterestRate
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember 		               
Additional borrowing capacity available provided there is no default under the agreement 180,000,000ofc_CreditFacilityAdditionalBorrowingCapacityAvailable
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember 		    180,000,000ofc_CreditFacilityAdditionalBorrowingCapacityAvailable
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember 		               
4.25% Exchangeable Senior Notes                        
Debt                        
Debt, net 572,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		563,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		  572,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		               
Stated interest rate (as a percent) 4.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		    4.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		      4.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		       
Interest rate on debt (as a percent) 6.05%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		    6.05%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		               
Unamortized discount included in carrying value 3,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		12,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		  3,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		               
Initial amount borrowed               240,000,000us-gaap_ProceedsFromIssuanceOfDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		       
Exchange rate per $1000 principal amount (in common shares) 20.8513us-gaap_DebtInstrumentConvertibleConversionRatio1
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		                     
Convertible debt principal amount, basis for exchange 1,000ofc_DebtInstrumentExchangeRatePrincipalAmountUsedInCalculation
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		    1,000ofc_DebtInstrumentExchangeRatePrincipalAmountUsedInCalculation
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		               
Exchange price per common share based on exchange rate (in dollars per share) $ 47.96us-gaap_DebtInstrumentConvertibleConversionPrice1
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		    $ 47.96us-gaap_DebtInstrumentConvertibleConversionPrice1
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		               
Percentage over the entity's common stock price at the time of issuance which was used to determine the initial exchange rate 20.00%ofc_DebtInstrumentConvertibleExchangeRatePercentageOverEntityCommonStockPriceClosingPriceAtIssuance
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		                     
Repurchase of notes, percentage of principal paid 100.00%ofc_RepurchaseOfExchangeableSeniorNotesPercentageOfPrincipalPaid
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		    100.00%ofc_RepurchaseOfExchangeableSeniorNotesPercentageOfPrincipalPaid
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		               
Amount of loans repaid upon entry into Revolving Credit Facility and Term Loan Agreement   239,400,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		                   
Loss on early extinguishment of debt   25,900,000us-gaap_GainsLossesOnExtinguishmentOfDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		                   
Principal amount of debt 575,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		575,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		  575,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		               
Interest expense at stated interest rate 24,000us-gaap_InterestExpenseDebtExcludingAmortization
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		4,208,000us-gaap_InterestExpenseDebtExcludingAmortization
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		10,200,000us-gaap_InterestExpenseDebtExcludingAmortization
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		                 
Interest expense associated with amortization of discount 10,000us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		1,615,000us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		3,651,000us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		                 
Total interest expenses 34,000us-gaap_InterestExpenseDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		5,823,000us-gaap_InterestExpenseDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		13,851,000us-gaap_InterestExpenseDebt
/ us-gaap_DebtInstrumentAxis
= ofc_Exchangeable425PercentSeniorNotesMember 		                 
Unsecured notes payable                        
Debt                        
Debt, net 1,607,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember 		1,700,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember 		  1,607,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember 		               
Stated interest rate (as a percent) 0.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember 		    0.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember 		               
Unamortized discount included in carrying value 654,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember 		761,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember 		  654,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= us-gaap_UnsecuredDebtMember 		               
Debt in Default of Payment Terms                        
Debt                        
Number of real estate properties 2us-gaap_NumberOfRealEstateProperties
/ us-gaap_DebtInstrumentAxis
= ofc_DebtinDefaultofPaymentTermsMember 		    2us-gaap_NumberOfRealEstateProperties
/ us-gaap_DebtInstrumentAxis
= ofc_DebtinDefaultofPaymentTermsMember 		               
Senior Notes                        
Debt                        
Redemption percentage within three months of maturity 100.00%ofc_RedemptionPercentageWithinThreeMonthsofMaturity
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		                     
Senior Notes | 3.60% Senior Notes                        
Debt                        
Debt, net 347,496,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		347,244,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		  347,496,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		               
Stated interest rate (as a percent) 3.60%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		    3.60%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		        3.60%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		     
Interest rate on debt (as a percent) 3.70%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		    3.70%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		               
Unamortized discount included in carrying value 2,500,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		2,800,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		  2,500,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		               
Initial amount borrowed                 347,100,000us-gaap_ProceedsFromIssuanceOfDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		     
Loan amount                 350,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		     
Debt issuance as a percentage of principal amount                 99.82%ofc_Debtissuanceasapercentageofprincipalamount
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		     
Senior Notes | 5.250% Senior Notes                        
Debt                        
Debt, net 245,797,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		245,445,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		  245,797,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		               
Stated interest rate (as a percent) 5.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		    5.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		          5.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		   
Interest rate on debt (as a percent) 5.49%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		    5.49%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		               
Unamortized discount included in carrying value 4,200,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
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/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		  4,200,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		               
Initial amount borrowed                   245,300,000us-gaap_ProceedsFromIssuanceOfDebt
/ us-gaap_DebtInstrumentAxis
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/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		   
Loan amount                   250,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		   
Debt issuance as a percentage of principal amount                   98.78%ofc_Debtissuanceasapercentageofprincipalamount
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		   
Senior Notes | 3.70% Senior Notes                        
Debt                        
Debt, net 297,569,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
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/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		0us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		  297,569,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		               
Stated interest rate (as a percent)                     3.70%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
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/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		 
Interest rate on debt (as a percent) 3.85%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		    3.85%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		               
Unamortized discount included in carrying value 2,400,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_DebtInstrumentAxis
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/ us-gaap_LongtermDebtTypeAxis
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/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		               
Initial amount borrowed                     297,300,000us-gaap_ProceedsFromIssuanceOfDebt
/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		 
Loan amount                     300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		 
Debt issuance as a percentage of principal amount                     99.74%ofc_Debtissuanceasapercentageofprincipalamount
/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		 
London Interbank Offered Rate (LIBOR) | Term Credit Facility Effective September 2011                        
Debt                        
Description of variable rate basis LIBOR                      
London Interbank Offered Rate (LIBOR) | Term Credit Facility Effective February 2012                        
Debt                        
Description of variable rate basis LIBOR                      
London Interbank Offered Rate (LIBOR) | Term Credit Facility Effective August 2012                        
Debt                        
Description of variable rate basis LIBOR                      
Adjusted Treasury | Senior Notes | 3.60% Senior Notes                        
Debt                        
Basis points used in determining redemption price prior to maturity 30.00%ofc_Basispointsusedindeterminingredemptionpricepriortomaturity
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
/ us-gaap_VariableRateAxis
= ofc_AdjustedTreasuryMember 		    30.00%ofc_Basispointsusedindeterminingredemptionpricepriortomaturity
/ us-gaap_DebtInstrumentAxis
= ofc_A3.60SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
/ us-gaap_VariableRateAxis
= ofc_AdjustedTreasuryMember 		               
Adjusted Treasury | Senior Notes | 5.250% Senior Notes                        
Debt                        
Basis points used in determining redemption price prior to maturity 40.00%ofc_Basispointsusedindeterminingredemptionpricepriortomaturity
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
/ us-gaap_VariableRateAxis
= ofc_AdjustedTreasuryMember 		    40.00%ofc_Basispointsusedindeterminingredemptionpricepriortomaturity
/ us-gaap_DebtInstrumentAxis
= ofc_A5.250SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
/ us-gaap_VariableRateAxis
= ofc_AdjustedTreasuryMember 		               
Adjusted Treasury | Senior Notes | 3.70% Senior Notes                        
Debt                        
Basis points used in determining redemption price prior to maturity 25.00%ofc_Basispointsusedindeterminingredemptionpricepriortomaturity
/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
/ us-gaap_VariableRateAxis
= ofc_AdjustedTreasuryMember 		    25.00%ofc_Basispointsusedindeterminingredemptionpricepriortomaturity
/ us-gaap_DebtInstrumentAxis
= ofc_A3.70SeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
/ us-gaap_VariableRateAxis
= ofc_AdjustedTreasuryMember 		               
Revolving Credit Facility | Revolving Credit Facility                        
Debt                        
Maximum Availability 800,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		    800,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		               
Weighted average interest rate (as a percent) 1.47%us-gaap_DebtWeightedAverageInterestRate
/ us-gaap_CreditFacilityAxis
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/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		1.74%us-gaap_DebtWeightedAverageInterestRate
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= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		  1.47%us-gaap_DebtWeightedAverageInterestRate
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		               
Expansion right, maximum borrowing capacity 1,300,000,000ofc_LineOfCreditExpansionRightMaximumBorrowingAvailabiliity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		    1,300,000,000ofc_LineOfCreditExpansionRightMaximumBorrowingAvailabiliity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		               
Amount available as a percentage of unencumbered Asset value 60.00%ofc_LineOfCreditFacilityPercentageOfUnencumberedAssetValue
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		                     
Extension option period (in years) 1 year                      
Line of credit facility, extension fee percentage 0.15%ofc_LineofCreditFacilityExtensionFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		                     
Remaining borrowing capacity 702,200,000us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		    702,200,000us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		               
Weighted average borrowings 15,900,000us-gaap_LineOfCreditFacilityAverageOutstandingAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		55,500,000us-gaap_LineOfCreditFacilityAverageOutstandingAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember 		                   
Minimum | Revolving Credit Facility                        
Debt                        
Variable rate, spread (as a percent) 0.975%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember 		                     
Minimum | Term Loan Facilities                        
Debt                        
Variable rate, spread (as a percent) 1.10%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember 		[4]                      
Minimum | London Interbank Offered Rate (LIBOR) | Term Credit Facility Effective September 2011                        
Debt                        
Variable rate, spread (as a percent) 1.10%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveSeptember2011Member
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember 		                     
Minimum | London Interbank Offered Rate (LIBOR) | Term Credit Facility Effective February 2012                        
Debt                        
Variable rate, spread (as a percent) 1.10%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveFebruary2012Member
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember 		                     
Minimum | London Interbank Offered Rate (LIBOR) | Term Credit Facility Effective August 2012                        
Debt                        
Variable rate, spread (as a percent) 2.10%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
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/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember 		                     
Minimum | Revolving Credit Facility | Revolving Credit Facility                        
Debt                        
Commitment fee percentage 0.125%us-gaap_LineOfCreditFacilityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember 		                     
Minimum | Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility                        
Debt                        
Variable rate, spread (as a percent) 0.975%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember 		                     
Maximum | Fixed rate mortgage loans                        
Debt                        
Stated interest rate excluding incremental rate on default rate 7.87%ofc_DebtInstrumentInterestRateStatedPercentageExcludingIncrementalRateOnDefaultRate
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		    7.87%ofc_DebtInstrumentInterestRateStatedPercentageExcludingIncrementalRateOnDefaultRate
/ us-gaap_DebtInstrumentAxis
= ofc_FixedRateSecuredDebtMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		               
Maximum | Revolving Credit Facility                        
Debt                        
Variable rate, spread (as a percent) 1.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		                     
Maximum | Term Loan Facilities                        
Debt                        
Variable rate, spread (as a percent) 2.60%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_TermLoanFacilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		[4]                      
Maximum | London Interbank Offered Rate (LIBOR) | Term Credit Facility Effective September 2011                        
Debt                        
Variable rate, spread (as a percent) 2.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveSeptember2011Member
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember 		                     
Maximum | London Interbank Offered Rate (LIBOR) | Term Credit Facility Effective February 2012                        
Debt                        
Variable rate, spread (as a percent) 2.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveFebruary2012Member
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember 		                     
Maximum | London Interbank Offered Rate (LIBOR) | Term Credit Facility Effective August 2012                        
Debt                        
Variable rate, spread (as a percent) 2.60%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= ofc_TermCreditFacilityEffectiveAugust2012Member
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember 		                     
Maximum | Revolving Credit Facility | Revolving Credit Facility                        
Debt                        
Commitment fee percentage 0.35%us-gaap_LineOfCreditFacilityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		                     
Maximum | Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility                        
Debt                        
Variable rate, spread (as a percent) 1.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
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/ us-gaap_DebtInstrumentAxis
= ofc_CreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember 		                     
Wholly Owned Subsidiary                        
Debt                        
Debt, net $ 150,000,000us-gaap_DebtDefaultLongtermDebtAmount
/ dei_LegalEntityAxis
= ofc_WhollyOwnedSubsidiaryMember 		    $ 150,000,000us-gaap_DebtDefaultLongtermDebtAmount
/ dei_LegalEntityAxis
= ofc_WhollyOwnedSubsidiaryMember 		              $ 150,000,000us-gaap_DebtDefaultLongtermDebtAmount
/ dei_LegalEntityAxis
= ofc_WhollyOwnedSubsidiaryMember
Wholly Owned Subsidiary | Debt in Default of Payment Terms                        
Debt                        
Stated interest rate (as a percent)                       10.65%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ofc_DebtinDefaultofPaymentTermsMember
/ dei_LegalEntityAxis
= ofc_WhollyOwnedSubsidiaryMember
Northern Virginia | Wholly Owned Subsidiary | Debt in Default of Payment Terms                        
Debt                        
Number of real estate properties                       2us-gaap_NumberOfRealEstateProperties
/ us-gaap_DebtInstrumentAxis
= ofc_DebtinDefaultofPaymentTermsMember
/ dei_LegalEntityAxis
= ofc_WhollyOwnedSubsidiaryMember
/ us-gaap_StatementGeographicalAxis
= ofc_NorthernVirginiaMember
[1] Represents scheduled principal amortization and maturities only and therefore excludes net discounts of $9.8 million.
[2] The interest rate on the loan outstanding was 2.41% as of December 31, 2014.
[3] Refer to the paragraphs below for further disclosure.
[4] These notes carry interest rates that were below market rates upon assumption and therefore were recorded at their fair value based on applicable effective interest rates. The carrying value of these notes reflects an unamortized discount totaling $654,000 as of December 31, 2014 and $761,000 as of December 31, 2013.