Annual report pursuant to Section 13 and 15(d)

Real Estate Investments - Noncontrolling Interests in Subsidiaries and VIEs (Details)

v2.4.0.6
Real Estate Investments - Noncontrolling Interests in Subsidiaries and VIEs (Details) (USD $)
12 Months Ended 6 Months Ended 1 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Aug. 31, 2007
4661 Kenmore Avenue [Member]
acre
Jun. 30, 2011
Six Fifty North Glebe Road [Member]
Dec. 31, 2012
Six Fifty North Glebe Road [Member]
Dec. 31, 2011
Six Fifty North Glebe Road [Member]
Nov. 30, 2011
1225 First Street [Member]
Dec. 31, 2012
1225 First Street [Member]
Dec. 31, 2011
1225 First Street [Member]
Oct. 31, 2011
Northern Virginia Industrial Park I I Member
Dec. 31, 2012
Minimum [Member]
Dec. 31, 2012
Maximum [Member]
Real Estate Properties [Line Items]                          
Land, Acres Held       0.8                  
Gain on sale of properties $ 5,124,000 $ 97,491,000 $ 21,599,000               $ 400,000    
Estimated development costs         49,500,000     95,300,000          
Percentage of capital contribution through debt 70.00%       70.00%     70.00%          
Ownership percentage         90.00%     95.00%       90.00% 95.00%
Percentage Of residential property to be leased to achieve project stabilization stage         90.00%                
Ownership percentage by noncontrolling owners         10.00%     5.00%          
Land and capitalized development costs           15,646,000 13,406,000   19,807,000 14,396,000      
Accounts payable and accrued liabilities $ 52,823,000 $ 51,079,000       $ 115,000 $ 47,000   $ 1,676,000 $ 235,000