Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements (Details 2)

v2.4.1.9
Fair Value Measurements (Details 2) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Liabilities:        
Interest rate derivatives $ 1,855us-gaap_InterestRateDerivativeLiabilitiesAtFairValue $ 3,309us-gaap_InterestRateDerivativeLiabilitiesAtFairValue    
Redeemable noncontrolling interest 18,417us-gaap_RedeemableNoncontrollingInterestEquityFairValue 17,758us-gaap_RedeemableNoncontrollingInterestEquityFairValue 10,298us-gaap_RedeemableNoncontrollingInterestEquityFairValue 8,908us-gaap_RedeemableNoncontrollingInterestEquityFairValue
Corporate Office Properties, L.P.        
Liabilities:        
Interest rate derivatives 1,855us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		3,309us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		   
Fair value measurement on a recurring basis        
Assets:        
Common stocks   298us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1]    
Interest rate derivatives 274us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[2] 6,594us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[2]    
Warrants to purchase common stock in KEYW 164ofc_WarrantsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[2] 301ofc_WarrantsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[2]    
Assets 6,320us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		14,660us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Liabilities:        
Deferred compensation plan liability 5,882us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[3] 7,467us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[3]    
Interest rate derivatives 1,855us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		3,309us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Liabilities 7,737us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		10,776us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Redeemable noncontrolling interest 18,417us-gaap_RedeemableNoncontrollingInterestEquityFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		17,758us-gaap_RedeemableNoncontrollingInterestEquityFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Fair value measurement on a recurring basis | Mutual funds        
Assets:        
Marketable securities in deferred compensation plan 5,756us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquityFundsMember 		[1] 7,090us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquityFundsMember 		[1]    
Fair value measurement on a recurring basis | Common Shares        
Assets:        
Marketable securities in deferred compensation plan   176us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember 		[1]    
Fair value measurement on a recurring basis | Other        
Assets:        
Marketable securities in deferred compensation plan 126us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= ofc_OtherMarketableSecuritiesMember 		[1] 201us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= ofc_OtherMarketableSecuritiesMember 		[1]    
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)        
Assets:        
Common stocks   298us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1]    
Assets 5,882us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		7,765us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Liabilities:        
Liabilities 0us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		0us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual funds        
Assets:        
Marketable securities in deferred compensation plan 5,756us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquityFundsMember 		[1] 7,090us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_EquityFundsMember 		[1]    
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Common Shares        
Assets:        
Marketable securities in deferred compensation plan   176us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember 		[1]    
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other        
Assets:        
Marketable securities in deferred compensation plan 126us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= ofc_OtherMarketableSecuritiesMember 		[1] 201us-gaap_DeferredCompensationPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= ofc_OtherMarketableSecuritiesMember 		[1]    
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2)        
Assets:        
Interest rate derivatives 274us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[2] 6,594us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[2]    
Warrants to purchase common stock in KEYW 164ofc_WarrantsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[2] 301ofc_WarrantsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[2]    
Assets 438us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		6,895us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Liabilities:        
Deferred compensation plan liability 5,882us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[3] 7,467us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[3]    
Interest rate derivatives 1,855us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		3,309us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Liabilities 7,737us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		10,776us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Fair value measurement on a recurring basis | Significant Unobservable Inputs (Level 3)        
Liabilities:        
Redeemable noncontrolling interest 18,417us-gaap_RedeemableNoncontrollingInterestEquityFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		17,758us-gaap_RedeemableNoncontrollingInterestEquityFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		   
Fair value measurement on a recurring basis | Corporate Office Properties, L.P.        
Assets:        
Common stocks   298us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[4]    
Interest rate derivatives 274us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[5] 6,594us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[5]    
Warrants to purchase common stock in KEYW 164ofc_WarrantsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[5] 301ofc_WarrantsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[5]    
Assets 438us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		7,193us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		   
Liabilities:        
Interest rate derivatives 1,855us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		3,309us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		   
Redeemable noncontrolling interest 18,417us-gaap_RedeemableNoncontrollingInterestEquityFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		17,758us-gaap_RedeemableNoncontrollingInterestEquityFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		   
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Quoted Prices in Active Markets for Identical Assets (Level 1)        
Assets:        
Common stocks   298us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[4]    
Assets 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		298us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		   
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2)        
Assets:        
Interest rate derivatives 274us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[5] 6,594us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[5]    
Warrants to purchase common stock in KEYW 164ofc_WarrantsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[5] 301ofc_WarrantsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[5]    
Assets 438us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		6,895us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		   
Liabilities:        
Interest rate derivatives 1,855us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		3,309us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		   
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Unobservable Inputs (Level 3)        
Assets:        
Assets 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		   
Liabilities:        
Redeemable noncontrolling interest $ 18,417us-gaap_RedeemableNoncontrollingInterestEquityFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 17,758us-gaap_RedeemableNoncontrollingInterestEquityFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		   
[1] Included in the line entitled “restricted cash and marketable securities” on COPT’s consolidated balance sheet.
[2] Included in the line entitled “prepaid expenses and other assets” on COPT’s consolidated balance sheet.
[3] Included in the line entitled “other liabilities” on COPT’s consolidated balance sheet.
[4] Included in the line entitled “restricted cash and marketable securities” on COPLP’s consolidated balance sheet.
[5] Included in the line entitled “prepaid expenses and other assets” on COPLP’s consolidated balance sheet.