Quarterly report pursuant to Section 13 or 15(d)

Investments In Unconsolidated Joint Ventures (Summary Of Company's Equity In Earnings (Loss) Of Unconsolidated Joint Ventures) (Details)

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Investments In Unconsolidated Joint Ventures (Summary Of Company's Equity In Earnings (Loss) Of Unconsolidated Joint Ventures) (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Mar. 12, 2020
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ (1,456) $ (708)    
Amortization of basis difference 143 152    
Unconsolidated Joint Venture Multi-Family Properties [Member] | Metropolitan And Lofts At 40 Park [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ (231) (140)    
Company's Effective Ownership % 25.00%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | RiverTrace At Port Imperial [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ (5) 98    
Company's Effective Ownership % 22.50%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | Crystal House [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures   (159)    
Gain on sale     $ 35,100  
Unconsolidated Joint Venture Multi-Family Properties [Member] | Riverpark At Harrison [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ (50) (58)    
Company's Effective Ownership % 45.00%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | Station House [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ (364) (467)    
Company's Effective Ownership % 50.00%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | Urby At Harborside [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ (745) 17    
Company's Effective Ownership % 85.00%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | PI North Pier Land [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ (57) (119)    
Unconsolidated Joint Venture Office Buildings [Member] | 12 Vreeland Road [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures   111    
Company's Effective Ownership % 50.00%      
Unconsolidated Joint Venture Office Buildings [Member] | Offices At Crystal Lake [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ (118) 20    
Company's Effective Ownership % 31.25%      
Unconsolidated Joint Venture Other Property [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ (1,456) (708)    
Unconsolidated Joint Venture Other Property [Member] | Riverwalk Retail [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures   $ (11)    
Company's Effective Ownership %       80.00%
Unconsolidated Joint Venture Other Property [Member] | Other [Member]        
Schedule of Equity Method Investments [Line Items]        
Company's equity in earnings (loss) of unconsolidated joint ventures $ 114