Mortgages, Loans Payable And Other Obligations (Summary Of Mortgages, Loans Payable And Other Obligations) (Details)
1 Months Ended 3 Months Ended
Jan. 31, 2020
USD ($)
Mar. 31, 2020
USD ($)
item
Mar. 31, 2019
USD ($)
Dec. 31, 2019
USD ($)
Debt Instrument [Line Items]        
Principal balance outstanding   $ 2,877,121,000   $ 2,808,517,000
Borrowings from revolving credit facility   69,000,000 $ 92,000,000  
Payment for borrowings   $ 121,000,000 $ 204,000,000  
Secured Debt [Member]        
Debt Instrument [Line Items]        
Effective rate   1.84%    
Principal balance outstanding   $ 2,045,152,000   1,925,038,000
Unamortized deferred financing costs   (16,807,000)   (17,004,000)
Total mortgages, loans payable and other obligations, net   $ 2,028,345,000   1,908,034,000
Secured Debt [Member] | Monaco [Member]        
Debt Instrument [Line Items]        
Property Name   Monaco (b)    
Lender   The Northwestern Mutual Life Insurance Co.    
Effective rate   3.15%    
Principal balance outstanding   $ 166,347,000   166,752,000
Loan maturity date   Feb. 01, 2021    
Secured Debt [Member] | Monaco [Member] | Construction Loan [Member]        
Debt Instrument [Line Items]        
Maximum borrowing capacity   $ 1,300,000    
Secured Debt [Member] | Port Imperial South 4/5 Retail [Member]        
Debt Instrument [Line Items]        
Property Name   Port Imperial South 4/5 Retail    
Lender   American General Life & A/G PC    
Effective rate   4.56%    
Principal balance outstanding   $ 3,918,000   3,934,000
Loan maturity date   Dec. 01, 2021    
Secured Debt [Member] | Port Imperial 4/5 Hotel [Member]        
Debt Instrument [Line Items]        
Property Name   Port Imperial 4/5 Hotel (c)    
Lender   Fifth Third Bank    
Effective rate   3.40%    
Principal balance outstanding   $ 94,000,000   74,000,000
Loan maturity date   Apr. 09, 2022    
Secured Debt [Member] | Port Imperial 4/5 Hotel [Member] | Construction Loan [Member]        
Debt Instrument [Line Items]        
Maximum borrowing capacity   $ 94,000,000    
Secured Debt [Member] | Emery At Overlook Ridge [Member]        
Debt Instrument [Line Items]        
Property Name   Emery at Overlook Ridge (d)    
Lender   Fifth Third Bank    
Effective rate   2.50%    
Principal balance outstanding   $ 42,136,000   24,064,000
Loan maturity date   May 16, 2022    
Secured Debt [Member] | Emery At Overlook Ridge [Member] | Construction Loan [Member]        
Debt Instrument [Line Items]        
Maximum borrowing capacity   $ 62,000,000    
Number of extension options | item   1    
Loan extension period   18 months    
Extension fee   0.25%    
Secured Debt [Member] | Port Imperial South 9 [Member]        
Debt Instrument [Line Items]        
Property Name   Port Imperial South 9 (e)    
Lender   Bank of New York Mellon    
Effective rate   2.13%    
Principal balance outstanding   $ 19,624,000   11,615,000
Loan maturity date   Dec. 19, 2022    
Secured Debt [Member] | Port Imperial South 9 [Member] | Construction Loan [Member]        
Debt Instrument [Line Items]        
Maximum borrowing capacity   $ 92,000,000    
Number of extension options | item   1    
Loan extension period   1 year    
Extension fee   0.15%    
Secured Debt [Member] | Portside 7 [Member]        
Debt Instrument [Line Items]        
Property Name   Portside 7    
Lender   CBRE Capital Markets/FreddieMac    
Effective rate   3.57%    
Principal balance outstanding   $ 58,998,000   58,998,000
Loan maturity date   Aug. 01, 2023    
Secured Debt [Member] | Short Hills Residential [Member]        
Debt Instrument [Line Items]        
Property Name   Short Hills Residential (f)    
Lender   People's United Bank    
Effective rate   2.15%    
Principal balance outstanding   $ 17,791,000   9,431,000
Loan maturity date   Mar. 26, 2023    
Secured Debt [Member] | Short Hills Residential [Member] | Construction Loan [Member]        
Debt Instrument [Line Items]        
Number of extension options | item   1    
Loan extension period   18 months    
Secured Debt [Member] | 250 Johnson Road [Member]        
Debt Instrument [Line Items]        
Property Name   250 Johnson    
Lender   Nationwide Life Insurance Company    
Effective rate   3.74%    
Principal balance outstanding   $ 43,000,000   43,000,000
Loan maturity date   Aug. 01, 2024    
Secured Debt [Member] | Liberty Towers [Member]        
Debt Instrument [Line Items]        
Property Name   Liberty Towers (g)    
Lender   American General Life Insurance Company    
Effective rate   3.37%    
Principal balance outstanding   $ 265,000,000   232,000,000
Loan maturity date   Oct. 01, 2024    
Secured Debt [Member] | Liberty Towers [Member] | Construction Loan [Member]        
Debt Instrument [Line Items]        
Payment for borrowings $ 265,000,000      
Additional borrowing capacity $ 33,000,000      
Secured Debt [Member] | The Charlotte [Member]        
Debt Instrument [Line Items]        
Property Name   The Charlotte (h)    
Lender   QuadReal Finance    
Effective rate   2.70%    
Principal balance outstanding   $ 38,361,000   5,144,000
Loan maturity date   Dec. 01, 2024    
Secured Debt [Member] | The Charlotte [Member] | Construction Loan [Member]        
Debt Instrument [Line Items]        
Spread over LIBOR   2.00%    
Maximum borrowing capacity   $ 300,000,000    
Number of extension options | item   1    
Loan extension period   1 year    
Extension fee   0.25%    
Secured Debt [Member] | Portside 5/6 [Member]        
Debt Instrument [Line Items]        
Property Name   Portside 5/6    
Lender   New York Life Insurance Company    
Effective rate   4.56%    
Principal balance outstanding   $ 97,000,000   97,000,000
Loan maturity date   Mar. 10, 2026    
Secured Debt [Member] | Marbella I [Member]        
Debt Instrument [Line Items]        
Property Name   Marbella    
Lender   New York Life Insurance Company    
Effective rate   4.17%    
Principal balance outstanding   $ 131,000,000   131,000,000
Loan maturity date   Aug. 10, 2026    
Secured Debt [Member] | Marbella II [Member]        
Debt Instrument [Line Items]        
Property Name   Marbella II    
Lender   New York Life Insurance Company    
Effective rate   4.29%    
Principal balance outstanding   $ 117,000,000   117,000,000
Loan maturity date   Aug. 10, 2026    
Secured Debt [Member] | 101 Hudson [Member]        
Debt Instrument [Line Items]        
Property Name   101 Hudson    
Lender   Wells Fargo CMBS    
Effective rate   3.20%    
Principal balance outstanding   $ 250,000,000   250,000,000
Loan maturity date   Oct. 11, 2026    
Secured Debt [Member] | Worcester [Member]        
Debt Instrument [Line Items]        
Property Name   Worcester    
Lender   MUFG Union Bank    
Effective rate   1.84%    
Principal balance outstanding   $ 63,000,000   63,000,000
Loan maturity date   Dec. 10, 2026    
Secured Debt [Member] | Short Hills Residential [Member]        
Debt Instrument [Line Items]        
Property Name   Short Hills Portfolio (i)    
Lender   Wells Fargo CMBS    
Effective rate   4.15%    
Principal balance outstanding   $ 124,500,000   124,500,000
Loan maturity date   Apr. 01, 2027    
Secured Debt [Member] | Short Hills Residential [Member] | Construction Loan [Member]        
Debt Instrument [Line Items]        
Maximum borrowing capacity   $ 64,000,000    
Extension fee   0.30%    
Secured Debt [Member] | 150 Main St [Member]        
Debt Instrument [Line Items]        
Property Name   150 Main St.    
Lender   Natixis Real Estate Capital LLC    
Effective rate   4.48%    
Principal balance outstanding   $ 41,000,000   41,000,000
Loan maturity date   Aug. 05, 2027    
Secured Debt [Member] | Port Imperial South 11 [Member]        
Debt Instrument [Line Items]        
Property Name   Port Imperial South 11    
Lender   The Northwestern Mutual Life Insurance Co.    
Effective rate   4.52%    
Principal balance outstanding   $ 100,000,000   100,000,000
Loan maturity date   Jan. 10, 2029    
Secured Debt [Member] | Soho Lofts Apartments [Member]        
Debt Instrument [Line Items]        
Property Name   Soho Lofts (j)    
Lender   New York Community Bank    
Effective rate   3.77%    
Principal balance outstanding   $ 160,000,000   160,000,000
Loan maturity date   Jul. 01, 2029    
Secured Debt [Member] | Riverwatch Commons [Member]        
Debt Instrument [Line Items]        
Property Name   Riverwatch Commons (j)    
Lender   New York Community Bank    
Effective rate   3.79%    
Principal balance outstanding   $ 30,000,000   30,000,000
Loan maturity date   Jul. 01, 2029    
Effective percentage after five years   2.75%    
First period of term period   5 years    
Secured Debt [Member] | 111 River St. [Member]        
Debt Instrument [Line Items]        
Property Name   111 River St.    
Lender   Athene Annuity and Life Company    
Effective rate   3.90%    
Principal balance outstanding   $ 150,000,000   150,000,000
Loan maturity date   Sep. 01, 2029    
Secured Debt [Member] | Port Imperial South 4/5 Garage [Member]        
Debt Instrument [Line Items]        
Property Name   Port Imperial South 4/5 Garage    
Lender   American General Life & A/G PC    
Effective rate   4.85%    
Principal balance outstanding   $ 32,477,000   $ 32,600,000
Loan maturity date   Dec. 01, 2029