Quarterly report pursuant to Section 13 or 15(d)

Properties, net (Details 3)

v2.4.1.9
Properties, net (Details 3) (USD $)
0 Months Ended 3 Months Ended
Mar. 19, 2015
Mar. 31, 2015
Mar. 19, 2015
sqft
Business Acquisition [Line Items]      
Weighted average useful life   10 years  
Tenant relationship value      
Business Acquisition [Line Items]      
Weighted average useful life   8 years  
250 W Pratt St | Baltimore, Maryland      
Business Acquisition [Line Items]      
Square footage of real estate properties (in square feet) 367,000us-gaap_AreaOfRealEstateProperty
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
  367,000us-gaap_AreaOfRealEstateProperty
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
Acquired property percentage leased 96.20%ofc_AcquiredPropertyPercentageLeased
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
  96.20%ofc_AcquiredPropertyPercentageLeased
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
Total acquisition cost $ 61,900,000us-gaap_PaymentsToAcquireRealEstate
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
   
Land 8,057,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLand
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
  8,057,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLand
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
Building and improvements 34,740,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBuildings
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
  34,740,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBuildings
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
Intangible assets on real estate acquisitions 20,183,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
  20,183,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
Total assets 62,980,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
  62,980,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
Below-market leases (1,093,000)ofc_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedBelowmarketLeases
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
  (1,093,000)ofc_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedBelowmarketLeases
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
Total acquisition cost 61,887,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
  61,887,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
Finite-lived intangible assets acquired 20,183,000us-gaap_FinitelivedIntangibleAssetsAcquired1
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
   
Weighted average useful life 8 years    
Operating property acquisition costs   1,000,000us-gaap_BusinessCombinationAcquisitionRelatedCosts
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
 
250 W Pratt St | Baltimore, Maryland | Tenant relationship value      
Business Acquisition [Line Items]      
Finite-lived intangible assets acquired 7,252,000us-gaap_FinitelivedIntangibleAssetsAcquired1
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_CustomerRelationshipsMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
   
Weighted average useful life 11 years    
250 W Pratt St | Baltimore, Maryland | In-place lease value      
Business Acquisition [Line Items]      
Finite-lived intangible assets acquired 10,218,000us-gaap_FinitelivedIntangibleAssetsAcquired1
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_LeasesAcquiredInPlaceMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
   
Weighted average useful life 7 years    
250 W Pratt St | Baltimore, Maryland | Above market leases      
Business Acquisition [Line Items]      
Finite-lived intangible assets acquired $ 2,713,000us-gaap_FinitelivedIntangibleAssetsAcquired1
/ us-gaap_BusinessAcquisitionAxis
= ofc_A250WPrattStMember
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_AboveMarketLeasesMember
/ us-gaap_StatementGeographicalAxis
= ofc_BaltimoreMarylandMember
   
Weighted average useful life 4 years