Quarterly report pursuant to Section 13 or 15(d)

Properties, net (Details 4)

v2.4.1.9
Properties, net (Details 4) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
sqft
Property
Newly constructed properties placed in service  
Construction and Redevelopment Activities  
Square feet of properties placed in service 440,000ofc_SquareFeetofPropertiesPlacedinService
/ us-gaap_RealEstatePropertiesAxis
= ofc_NewlyConstructedPropertiesPlacedInServiceMember
Number of real estate properties placed in service 3ofc_NumberOfRealEstatePropertiesPlacedInService
/ us-gaap_RealEstatePropertiesAxis
= ofc_NewlyConstructedPropertiesPlacedInServiceMember
Properties under construction or contractually committed for construction  
Construction and Redevelopment Activities  
Number of real estate properties 7us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderConstructionOrContractuallyCommitedForConstructionMember
Square footage of real estate properties (in square feet) 1,100,000us-gaap_AreaOfRealEstateProperty
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderConstructionOrContractuallyCommitedForConstructionMember
Properties under construction or contractually committed for construction | Baltimore and Washington Corridor  
Construction and Redevelopment Activities  
Number of real estate properties 2us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderConstructionOrContractuallyCommitedForConstructionMember
/ ofc_RealEstatePropertyLocationAxis
= ofc_BaltimoreAndWashingtonCorridorMember
Properties under construction or contractually committed for construction | Northern Virginia  
Construction and Redevelopment Activities  
Number of real estate properties 4us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderConstructionOrContractuallyCommitedForConstructionMember
/ ofc_RealEstatePropertyLocationAxis
= ofc_NorthernVirginiaMember
Properties under construction or contractually committed for construction | Huntsville  
Construction and Redevelopment Activities  
Number of real estate properties 1us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderConstructionOrContractuallyCommitedForConstructionMember
/ ofc_RealEstatePropertyLocationAxis
= ofc_HuntsvilleMember
Properties redeveloped  
Construction and Redevelopment Activities  
Square feet of properties placed in service 111,000ofc_SquareFeetofPropertiesPlacedinService
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesRedevelopedMember
Properties under or approved for redevelopment  
Construction and Redevelopment Activities  
Number of real estate properties 5us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderorApprovedforRedevelopmentMember
Square footage of real estate properties (in square feet) 344,000us-gaap_AreaOfRealEstateProperty
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderorApprovedforRedevelopmentMember
Properties under or approved for redevelopment | Baltimore and Washington Corridor  
Construction and Redevelopment Activities  
Number of real estate properties 3us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderorApprovedforRedevelopmentMember
/ ofc_RealEstatePropertyLocationAxis
= ofc_BaltimoreAndWashingtonCorridorMember
Properties under or approved for redevelopment | Greater Philadelphia  
Construction and Redevelopment Activities  
Number of real estate properties 1us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderorApprovedforRedevelopmentMember
/ ofc_RealEstatePropertyLocationAxis
= ofc_GreaterPhiladelphiaMember
Properties under or approved for redevelopment | St Marys County  
Construction and Redevelopment Activities  
Number of real estate properties 1us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= ofc_PropertiesUnderorApprovedforRedevelopmentMember
/ ofc_RealEstatePropertyLocationAxis
= ofc_StMarysCountyMember
Non-operating properties  
Construction and Redevelopment Activities  
Sale price of land 18.1us-gaap_ProceedsFromSaleOfLandHeldforinvestment
/ ofc_RealEstatePropertyDisposalAxis
= ofc_NonOperatingPropertiesMember
Gain on sale 4.0ofc_GainOnSaleOfPropertiesSold
/ ofc_RealEstatePropertyDisposalAxis
= ofc_NonOperatingPropertiesMember
Partially operational properties  
Construction and Redevelopment Activities  
Number of real estate properties 1us-gaap_NumberOfRealEstateProperties
/ ofc_RealEstatePropertiesStatusAxis
= ofc_PartiallyOperationalPropertiesMember