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Subsequent Event (Details) - Jul. 27, 2015 - 1550 Westbranch Drive - Subsequent Event - Northern Virginia ft² in Thousands, $ in Millions | USD ($) ft²
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Subsequent Event [Line Items] |
Square footage of real estate properties (in square feet) | 160
Transaction value of operating property disposition | $ | $ 27.8

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- Definition Represents the total transaction value of operating property dispositions during the period. + References No definition available. + Details
Name: | ofc_TransactionValueofOperatingPropertyDispositions
Namespace Prefix: | ofc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Area of a real estate property. + References No definition available. + Details
Name: | us-gaap_AreaOfRealEstateProperty
Namespace Prefix: | us-gaap_
Data Type: | num:areaItemType
Balance Type: | na
Period Type: | instant

X
- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | ofc_RealEstatePropertyDisposalAxis=ofc_Number1550WestbranchDriveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_StatementGeographicalAxis=ofc_NorthernVirginiaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |