Quarterly report pursuant to Section 13 or 15(d)

Real Estate Acquisitions And Discontinued Operations (Operating Income (Loss) By Property Classified As Discontinued Operations) (Details)

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Real Estate Acquisitions And Discontinued Operations (Operating Income (Loss) By Property Classified As Discontinued Operations) (Details) (USD $)
In Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2011
Sep. 30, 2010
Sep. 30, 2011
Sep. 30, 2010
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Total 2011 Total 2010
Income from operations of properties held for sale $ 3,655 $ 3,565 $ 9,522 $ 11,047
Parklawn Plaza [Member]
       
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Office  
Income from operations of properties held for sale       132
Lexington Building [Member]
       
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Office  
Income from operations of properties held for sale       65
Saratoga Building [Member]
       
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Office  
Income from operations of properties held for sale       225
Charleston Business Center [Member]
       
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Industrial  
Income from operations of properties held for sale       370
The Ridges [Member]
       
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Office Office
Income from operations of properties held for sale   156   347
Ammendale I&II [Member]
       
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Industrial  
Income from operations of properties held for sale   217   733
Amvax [Member]
       
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Industrial  
Income from operations of properties held for sale   82   260
Dulles Station, Phase I [Member]
       
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Office  
Income from operations of properties held for sale   160 (468) 367
Industrial Portfolio [Member]
       
Real Estate Properties [Line Items]        
Real Estate and Accumulated Depreciation, Description of Property     Industrial/Office [1]  
Income from operations of properties held for sale $ 3,655 $ 2,950 $ 9,990 $ 8,548
[1] The Industrial Portfolio consists of every property in our industrial segment and two office properties (the Crescent and Albemarle Point). On September 2, 2011 we closed on the sale of industrial properties (8880 Gorman Road, Dulles South IV, Fullerton Business Center, Hampton Overlook, Alban Business Center, Pickett Industrial Park, Northern Virginia Industrial Park I, 270 Technology Park, Fullerton Industrial Center, Sully Square, 9950 Business Parkway, Hampton South and 8900 Telegraph Road) and two office properties (Crescent and Albemarle Point). We closed on the sales of the remaining properties in the Industrial Portfolio subsequent to the end of the 2011 Quarter.