Investments In Unconsolidated Joint Ventures (Riverpark At Harrison I, L.L.C.) (Narrative) (Details) (USD $)
 6 Months Ended 6 Months Ended 6 Months Ended 6 Months Ended
Jun. 30, 2013
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Jul. 15, 2013
Jun. 30, 2013
Riverpark At Harrison I, L.L.C. [Member]
Oct. 23, 2012
Riverpark At Harrison I, L.L.C. [Member]
Jun. 30, 2013
Riverpark At Harrison I, L.L.C. [Member]
Chall Enterprises, L.L.C. [Member]
Jun. 30, 2013
Riverpark At Harrison I, L.L.C. [Member]
Investor Group [Member]
Jun. 30, 2013
Riverpark Project [Member]
Jun. 30, 2013
Riverpark Project [Member]
Riverpark At Harrison I, L.L.C. [Member]
Oct. 23, 2012
Riverpark Project [Member]
Riverpark At Harrison I, L.L.C. [Member]
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Jun. 30, 2013
Construction Loan [Member]
Riverpark At Harrison I, L.L.C. [Member]
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Jun. 30, 2013
Construction Loan [Member]
Riverpark Project [Member]
Riverpark At Harrison I, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]                      
Percentage of interest in venture       36.00%              
Number of units                 141    
Total project costs               $ 28,200,000      
Percentage of capital required to fund project             40.50%        
Third party ownership percentage         36.00% 28.00%          
Maximum borrowing capacity $ 600,000,000 $ 600,000,000               $ 23,400,000 $ 23,400,000
Spread over LIBOR   1.25%               2.35%  
Loan maturity date                   Jun. 01, 2016  
Number of extension options 2                 2  
Loan extension period                   1 year  
Extension fee                   0.20%  
Percentage of debt guaranteed by the company                   25.00%  
Percentage of debt guaranteed by company after project completion and achievement of financial ratios                   10.00%  
Threshold of payment guarantee, debt service coverage ratio                   1.30  
Threshold of payment guarantee, loan-to-value ratio                   65.00%  
Holding and distribution pattern under operating agreement     In general, the operating agreement of Riverpark provides, among other things, for the distribution of net cash flow to the members in accordance with their ownership percentages.