Annual report pursuant to Section 13 and 15(d)

Real Estate Investments Noncontrolling Interests in Subsidiaries (Details)

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Real Estate Investments Noncontrolling Interests in Subsidiaries (Details) (USD $)
0 Months Ended 12 Months Ended 0 Months Ended 0 Months Ended 1 Months Ended
Jun. 15, 2011
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2011
4661 Kenmore Avenue [Member]
acre
Jun. 15, 2011
Six Fifty North Glebe Road [Member]
Dec. 31, 2011
Six Fifty North Glebe Road [Member]
Nov. 23, 2011
Braddock Gateway [Member]
Dec. 31, 2011
Braddock Gateway [Member]
Oct. 31, 2011
Northern Virginia Industrial Park I I Member
Real Estate Properties [Line Items]                    
Land, Acres Held         0.8          
Estimated Development Costs           $ 43,500,000   $ 95,000,000    
Percentage Of Capital Contribution Through Debt 70.00%         70.00%   70.00%    
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage           90.00%   95.00%    
Percentage Of Residential Property To Be Leased To Achieve Project Stabilization Stage           90.00%        
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners           10.00%   5.00%    
Inventory, Real Estate, Land and Land Development Costs             13,400,000   14,400,000  
Gain (Loss) on Sale of Properties   $ 97,491,000 $ 21,600,000 $ 13,300,000           $ 400,000