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Properties, net (Details 4) (USD $) | 9 Months Ended | 3 Months Ended
--- | --- | ---
Sep. 30, 2014 Operating properties, net buillding sqft | Sep. 30, 2014 Operating properties, net 4969 and 4979 Mercantile Rd buillding sqft | Sep. 30, 2014 Operating properties, net 9930 and 9940 Franklin Square buillding sqft | Sep. 30, 2014 Operating properties, net 5020, 5022, 5024 and 5026 Campbell Boulevard buillding sqft | Sep. 30, 2014 Non-operating Properties
Investments in real estate |  |  |  |  |
Number of Properties Disposed | 8 | 2 | 2 | 4 |
Total Rentable Square Feet | 302,958 | 96,721 | 71,992 | 134,245 |
Transaction Value of Operating Property Dispositions | $ 28,835,000 | $ 5,960,000 | $ 10,475,000 | $ 12,400,000 |
Gain on Sale | 5,095,000 | 2,126,000 | 2,303,000 | 666,000 | 5,500,000
Transaction Value of Non-operating Property Dispositions |  |  |  |  | $ 28,300,000

X
- Definition Represents the total gain recognized on properties sold during the period. + References No definition available. + Details
Name: | ofc_GainOnSaleOfPropertiesSold
Namespace Prefix: | ofc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Represents the number of properties disposed during the period. + References No definition available. + Details
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Namespace Prefix: | ofc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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

X
- 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

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

X
- Details
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