Annual report pursuant to Section 13 and 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 ($)
 12 Months Ended
Dec. 17, 2020
Feb. 28, 2019
Jan. 31, 2019
Jan. 30, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Mar. 12, 2020
Schedule of Equity Method Investments [Line Items]                
Company's equity in earnings (loss) of unconsolidated joint ventures         $ (3,832,000) $ (1,319,000) $ (127,000)  
Amortization of basis difference         581,000 638,000    
Crystal House [Member]                
Schedule of Equity Method Investments [Line Items]                
Gain on sale         35,100,000      
Hillsborough 206 [Member]                
Schedule of Equity Method Investments [Line Items]                
Gain on sale $ 100,000              
Unconsolidated Joint Venture Multi-Family Properties [Member] | Marbella [Member]                
Schedule of Equity Method Investments [Line Items]                
Company's equity in earnings (loss) of unconsolidated joint ventures             205,000  
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         $ (1,010,000) (422,000) (455,000)  
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         $ 111,000 317,000 154,000  
Company's Effective Ownership %         22.50%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | Marbella Tower Urban Renewal Associates South LLC [Member]                
Schedule of Equity Method Investments [Line Items]                
Percentage of additional interest acquired     50.00% 50.00%        
Company's Effective Ownership %     74.27% 24.27%        
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         $ (924,000) (687,000) (874,000)  
Company's Effective Ownership %         25.00%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | PI North - Riverwalk C [Member]                
Schedule of Equity Method Investments [Line Items]                
Company's equity in earnings (loss) of unconsolidated joint ventures         $ (368,000) (279,000) (126,000)  
Company's Effective Ownership %         40.00%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | Marbella II [Member]                
Schedule of Equity Method Investments [Line Items]                
Company's equity in earnings (loss) of unconsolidated joint ventures           (15,000) 35,000  
Percentage of additional interest acquired     50.00%          
Company's Effective Ownership %     74.27% 24.27%        
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         $ (273,000) (172,000) (232,000)  
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         $ (1,650,000) (2,000,000) (2,096,000)  
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         $ 1,095,000 1,587,000 (975,000)  
Economic tax credit certificate income         $ 2,600,000      
Period of venture agreement to sell economic tax credit         7 years      
Annual proceeds from economic tax credit         $ 3,000,000      
Total proceeds from economic tax credit         $ 21,000,000      
Company's Effective Ownership %         85.00%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | Liberty Landing [Member]                
Schedule of Equity Method Investments [Line Items]                
Company's equity in earnings (loss) of unconsolidated joint ventures         $ (5,000)   (5,000)  
Company's Effective Ownership %         50.00%      
Unconsolidated Joint Venture Multi-Family Properties [Member] | Hillsborough 206 [Member]                
Schedule of Equity Method Investments [Line Items]                
Company's equity in earnings (loss) of unconsolidated joint ventures             16,000  
Company's Effective Ownership %         50.00%      
Unconsolidated Joint Venture Office Buildings [Member] | Crystal House [Member]                
Schedule of Equity Method Investments [Line Items]                
Gain on sale         $ 35,100,000      
Unconsolidated Joint Venture Office Buildings [Member] | Red Bank [Member]                
Schedule of Equity Method Investments [Line Items]                
Company's equity in earnings (loss) of unconsolidated joint ventures           8,000 (215,000)  
Percentage of interest sold   50.00%            
Gain on sale   $ 900,000            
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         $ (2,035,000) (3,172,000) 285,000  
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         $ 224,000 79,000 73,000  
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         $ (3,832,000) (1,319,000) (127,000)  
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         $ (10,000) (72,000) (86,000)  
Company's Effective Ownership %         20.00%     80.00%
Unconsolidated Joint Venture Other Property [Member] | Hyatt Regency Hotel Jersey City [Member]                
Schedule of Equity Method Investments [Line Items]                
Company's equity in earnings (loss) of unconsolidated joint ventures         $ 625,000 3,388,000 3,672,000  
Company's Effective Ownership %         50.00%      
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         $ 388,000 $ 121,000 $ 497,000