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Properties, net (Details 3) (Linthicum Maryland, USD $) In Millions, unless otherwise specified | 9 Months Ended
--- | ---
Sep. 30, 2013 sqft
Linthicum Maryland |
Dispositions [Line Items] |
Square footage of real estate properties (in square feet) | 103,000
Sales Price of Operating Properties Sold | $ 6.9

X
- Definition Represents the total sales price of operating properties sold during the period. + References No definition available. + Details
Name: | ofc_SalesPriceOfOperatingPropertiesSold
Namespace Prefix: | ofc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | ofc_SignificantDisposalsLineItems
Namespace Prefix: | ofc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- 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