Annual report pursuant to Section 13 and 15(d)

Properties, net (Details)

v2.4.1.9
Properties, net (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Properties        
Gross $ 4,014,336us-gaap_RealEstateGrossAtCarryingValue [1],[2] $ 3,811,950us-gaap_RealEstateGrossAtCarryingValue $ 3,859,960us-gaap_RealEstateGrossAtCarryingValue $ 4,038,932us-gaap_RealEstateGrossAtCarryingValue
Operating properties, net 2,751,488us-gaap_RentalProperties 2,702,693us-gaap_RentalProperties    
Operating properties, net        
Properties        
Less: accumulated depreciation (703,083)us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation
/ ofc_RealEstatePropertiesStatusAxis
= ofc_OperatingPropertiesMember 		(597,649)us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation
/ ofc_RealEstatePropertiesStatusAxis
= ofc_OperatingPropertiesMember 		   
Operating properties, net | Land        
Properties        
Gross 439,355us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandMember
/ ofc_RealEstatePropertiesStatusAxis
= ofc_OperatingPropertiesMember 		430,472us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandMember
/ ofc_RealEstatePropertiesStatusAxis
= ofc_OperatingPropertiesMember 		   
Operating properties, net | Buildings and improvements        
Properties        
Gross $ 3,015,216us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_BuildingAndBuildingImprovementsMember
/ ofc_RealEstatePropertiesStatusAxis
= ofc_OperatingPropertiesMember 		$ 2,869,870us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_BuildingAndBuildingImprovementsMember
/ ofc_RealEstatePropertiesStatusAxis
= ofc_OperatingPropertiesMember 		   
[1] 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.
[2] The aggregate cost of these assets for Federal income tax purposes was approximately $3.4 billion at December 31, 2014.