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Properties, net (Details 5) | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2011 | Dec. 31, 2010
Fully operational office properties |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 2 |
Square footage of real estate properties (in square feet) | 228,000 |
Square feet placed in service on properties as of prior year end (in square feet) |  | 79,000
Fully operational office properties | Baltimore/Washington Corridor |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 1 |
Fully operational office properties | Greater Baltimore |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under construction |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 10 |
Square footage of real estate properties (in square feet) | 1,200,000 |
Properties under construction | Baltimore/Washington Corridor |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 4 |
Properties under construction | Greater Baltimore |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 2 |
Properties under construction | San Antonio |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under construction | Northern Virginia |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under construction | Huntsville |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under construction | St. Mary's County |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under development |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 8 |
Square footage of real estate properties (in square feet) | 1,000,000 |
Properties under development | Baltimore/Washington Corridor |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 3 |
Properties under development | San Antonio |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 2 |
Properties under development | Northern Virginia |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under development | Huntsville |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 2 |
Properties under redevelopment |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 2 |
Square footage of real estate properties (in square feet) | 297,000 |
Properties under redevelopment | Northern Virginia |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under redevelopment | Greater Philadelphia |  |
2011 Construction, Development and Redevelopment Activities |  |
Number of real estate properties | 1 |

X
- Definition The amount of square footage placed into service as of the prior year end on properties becoming fully operational during the current period. + Details
Name: | ofc_SquareFeetPlacedInServiceOnPropertiesAsOfPriorYearEnd
Namespace Prefix: | ofc
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of real estate properties owned as of the balance sheet date. + Details
Name: | us-gaap_NumberOfRealEstateProperties
Namespace Prefix: | us-gaap
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + Details
Name: | us-gaap_RealEstatePropertiesLineItems
Namespace Prefix: | us-gaap
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of square footage related to a real estate property. + Details
Name: | us-gaap_SquareFootageOfRealEstateProperty
Namespace Prefix: | us-gaap
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration