Quarterly report pursuant to Section 13 or 15(d)

Real Estate Acquisitions and Discontinued Operations (Real Estate Sold During 2011 and 2010) (Details)

 v2.3.0.11
Real Estate Acquisitions and Discontinued Operations (Real Estate Sold During 2011 and 2010) (Details) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2011
Aug. 05, 2011
Rental Square feet 638,000  
Contract Purchase Price $ 73.9 $ 350.0
Dulles Station, Phase I [Member]
   
Disposition Date April 5, 2011  
Property Type Office  
Rental Square feet 180,000  
Contract Purchase Price 58.8  
Parklawn Portfolio [Member]
   
Disposition Date June 18, 2010 [1]  
Property Type Office/Industrial [1]  
Rental Square feet 229,000 [1]  
Contract Purchase Price 23.4 [1]  
The Ridges [Member]
   
Disposition Date December 21, 2010  
Property Type Office  
Rental Square feet 104,000  
Contract Purchase Price 27.5  
Ammendale I&II and Amvax [Member]
   
Disposition Date December 22, 2010  
Property Type Industrial  
Rental Square feet 305,000  
Contract Purchase Price $ 23.0  
[1] The Parklawn Portfolio consists of three office properties (Parklawn Plaza, Lexington Building and Saratoga Building) and one industrial property (Charleston Business Center).