Quarterly report pursuant to Section 13 or 15(d)

Real Estate - Variable Interest Entities (Details)

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Real Estate - Variable Interest Entities (Details) (USD $)
9 Months Ended 1 Months Ended 3 Months Ended 9 Months Ended 1 Months Ended 9 Months Ended
Sep. 30, 2013
Jun. 30, 2011
650 North Glebe Road [Member]
Mar. 31, 2013
650 North Glebe Road [Member]
Sep. 30, 2013
650 North Glebe Road [Member]
Dec. 31, 2012
650 North Glebe Road [Member]
Nov. 30, 2011
1225 First Street [Member]
Sep. 30, 2013
1225 First Street [Member]
Dec. 31, 2012
1225 First Street [Member]
Real Estate Properties [Line Items]                
Estimated development costs   $ 49,900,000       $ 95,300,000    
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%  
Land and capitalized development costs related to joint ventures       24,185,000 15,646,000   21,409,000 19,807,000
Accounts payable and accrued liabilities related to joint ventures       $ 2,584,000 $ 115,000   $ 249,000 $ 1,676,000