XML 97 R63.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Properties, net (Details 6) | 12 Months Ended
--- | ---
Dec. 31, 2011 property sqfeet | Dec. 31, 2010 sqfeet property
Newly-constructed properties placed in service |  |
Construction and Redevelopment Activities |  |
Number of real estate properties placed into service | 7 | 9
Square feet placed in service on properties during the period (in square feet) | 566,000 | 816,000
Newly-constructed properties placed in service | Baltimore/Washington Corridor |  |
Construction and Redevelopment Activities |  |
Number of real estate properties placed into service | 3 | 3
Newly-constructed properties placed in service | Greater Baltimore |  |
Construction and Redevelopment Activities |  |
Number of real estate properties placed into service | 2 | 2
Newly-constructed properties placed in service | San Antonio |  |
Construction and Redevelopment Activities |  |
Number of real estate properties placed into service | 1 | 2
Newly-constructed properties placed in service | St. Mary's County |  |
Construction and Redevelopment Activities |  |
Number of real estate properties placed into service | 1 |
Newly-constructed properties placed in service | Colorado Springs |  |
Construction and Redevelopment Activities |  |
Number of real estate properties placed into service |  | 2
Properties under construction |  |
Construction and Redevelopment Activities |  |
Number of real estate properties | 6 |
Square footage of real estate properties (in square feet) | 789,000 |
Properties under construction | Baltimore/Washington Corridor |  |
Construction and Redevelopment Activities |  |
Number of real estate properties | 3 |
Properties under construction | Greater Baltimore |  |
Construction and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under construction | Northern Virginia |  |
Construction and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under construction | Huntsville |  |
Construction and Redevelopment Activities |  |
Number of real estate properties | 1 |
Properties under redevelopment |  |
Construction and Redevelopment Activities |  |
Square footage of real estate properties (in square feet) | 113,000 |
Properties under redevelopment | Greater Philadelphia |  |
Construction and Redevelopment Activities |  |
Number of real estate properties | 1 |

X
- Definition Represents the number of real estate properties placed in service during the year. + References No definition available. + Details
Name: | ofc_NumberOfRealEstatePropertiesPlacedInService
Namespace Prefix: | ofc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of square footage placed into service during the period. + References No definition available. + Details
Name: | ofc_SquareFeetOfPropertiesPlacedInService
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. + References No definition available. + Details
Name: | us-gaap_NumberOfRealEstateProperties
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- 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. + References No definition available. + Details
Name: | us-gaap_SquareFootageOfRealEstateProperty
Namespace Prefix: | us-gaap_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration