Mortgages, Loans Payable And Other Obligations (Summary Of Mortgages, Loans Payable And Other Obligations) (Details)
1 Months Ended 12 Months Ended
Dec. 31, 2020
USD ($)
Nov. 30, 2020
Jan. 31, 2020
USD ($)
Dec. 31, 2020
USD ($)
item
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Debt Instrument [Line Items]            
Principal balance outstanding $ 2,801,797,000     $ 2,801,797,000 $ 2,808,518,000  
Payment for borrowings       516,000,000 617,000,000 $ 494,000,000
Secured Debt [Member]            
Debt Instrument [Line Items]            
Principal balance outstanding 2,218,862,000     2,218,862,000 1,925,038,000  
Unamortized deferred financing costs (14,718,000)     (14,718,000) (17,004,000)  
Total mortgages, loans payable and other obligations, net $ 2,204,144,000     $ 2,204,144,000 1,908,034,000  
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%     4.56%    
Principal balance outstanding $ 3,866,000     $ 3,866,000 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 (b)    
Lender       Fifth Third Bank    
Effective rate 3.40%     3.40%    
Principal balance outstanding $ 94,000,000     $ 94,000,000 74,000,000  
Loan maturity date       Apr. 09, 2022    
Guaranteed amount $ 19,500,000     $ 19,500,000    
Secured Debt [Member] | Port Imperial South 9 [Member]            
Debt Instrument [Line Items]            
Property Name       Port Imperial South 9 (c)    
Lender       Bank of New York Mellon    
Effective rate 2.13%     2.13%    
Principal balance outstanding $ 46,357,000     $ 46,357,000 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     $ 92,000,000    
Number of extension options | item       1    
Loan extension period       1 year    
Extension fee       0.15%    
Percent of principal loan outstanding       10.00%    
Secured Debt [Member] | Portside 7 [Member]            
Debt Instrument [Line Items]            
Property Name       Portside 7    
Lender       CBRE Capital Markets/FreddieMac    
Effective rate 3.57%     3.57%    
Principal balance outstanding $ 58,998,000     $ 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 (d)    
Lender       People's United Bank    
Effective rate 2.15%     2.15%    
Principal balance outstanding $ 42,459,000     $ 42,459,000 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    
Percent of principal loan outstanding       15.00%    
Secured Debt [Member] | 250 Johnson Road [Member]            
Debt Instrument [Line Items]            
Property Name       250 Johnson    
Lender       Nationwide Life Insurance Company    
Effective rate 3.74%     3.74%    
Principal balance outstanding $ 43,000,000     $ 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 (e)    
Lender       American General Life Insurance Company    
Effective rate 3.37%     3.37%    
Principal balance outstanding $ 265,000,000     $ 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 (f)    
Lender       QuadReal Finance    
Effective rate 2.70%     2.70%    
Principal balance outstanding $ 161,544,000     $ 161,544,000 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     $ 300,000,000    
Number of extension options | item       1    
Loan extension period       1 year    
Extension fee       25.00%    
Secured Debt [Member] | Portside 5/6 [Member]            
Debt Instrument [Line Items]            
Property Name       Portside 5/6 (g)    
Lender       New York Life Insurance Company    
Effective rate 4.56%     4.56%    
Principal balance outstanding $ 97,000,000     $ 97,000,000 97,000,000  
Loan maturity date       Mar. 10, 2026    
Percent of principal loan outstanding       10.00%    
Secured Debt [Member] | Marbella [Member]            
Debt Instrument [Line Items]            
Property Name       Marbella (BLVD 425)    
Lender       New York Life Insurance Company    
Effective rate 4.17%     4.17%    
Principal balance outstanding $ 131,000,000     $ 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 (BLVD 401)    
Lender       New York Life Insurance Company    
Effective rate 4.29%     4.29%    
Principal balance outstanding $ 117,000,000     $ 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%     3.20%    
Principal balance outstanding $ 250,000,000     $ 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%     1.84%    
Principal balance outstanding $ 63,000,000     $ 63,000,000 63,000,000  
Loan maturity date       Dec. 10, 2026    
Secured Debt [Member] | Short Hills Portfolio [Member]            
Debt Instrument [Line Items]            
Property Name       Short Hills Portfolio (h)    
Lender       Wells Fargo CMBS    
Effective rate 4.15%     4.15%    
Principal balance outstanding $ 124,500,000     $ 124,500,000 124,500,000  
Loan maturity date       Apr. 01, 2027    
Secured Debt [Member] | Short Hills Portfolio [Member] | Construction Loan [Member]            
Debt Instrument [Line Items]            
Maximum borrowing capacity $ 64,000,000     $ 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%     4.48%    
Principal balance outstanding $ 41,000,000     $ 41,000,000 41,000,000  
Loan maturity date       Aug. 05, 2027    
Secured Debt [Member] | Monaco (BLVD 495 N/S) [Member]            
Debt Instrument [Line Items]            
Property Name       Monaco (BLVD 495 N/S) (l)    
Lender       The Northwestern Mutual Life Insurance Co.    
Effective rate 2.91%     2.91%    
Principal balance outstanding $ 165,000,000     $ 165,000,000 166,752,000  
Loan maturity date Nov. 10, 2027 Feb. 01, 2021   Nov. 10, 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%     4.52%    
Principal balance outstanding $ 100,000,000     $ 100,000,000 100,000,000  
Loan maturity date       Jan. 10, 2029    
Secured Debt [Member] | Soho Lofts [Member]            
Debt Instrument [Line Items]            
Property Name       Soho Lofts (i)    
Lender       New York Community Bank    
Effective rate 3.77%     3.77%    
Principal balance outstanding $ 160,000,000     $ 160,000,000 160,000,000  
Loan maturity date       Jul. 01, 2029    
First period of term period       5 years    
Secured Debt [Member] | Riverwatch Commons [Member]            
Debt Instrument [Line Items]            
Property Name       Riverwatch Commons    
Lender       New York Community Bank    
Principal balance outstanding         30,000,000  
Effective percentage after five years 2.75%     2.75%    
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%     3.90%    
Principal balance outstanding $ 150,000,000     $ 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 (j)    
Lender       American General Life & A/G PC    
Effective rate 4.85%     4.85%    
Principal balance outstanding $ 33,138,000     $ 33,138,000 32,600,000  
Loan maturity date       Dec. 01, 2029    
Deferred interest       $ 800,000    
Deferred interest and principal payment period       6 months    
Deferred interest and payment end date       Dec. 01, 2020    
Secured Debt [Member] | Emery At Overlook Ridge [Member]            
Debt Instrument [Line Items]            
Property Name       Emery at Overlook Ridge (k)    
Lender       New York Community Bank    
Effective rate 3.21%     3.21%    
Principal balance outstanding $ 72,000,000     $ 72,000,000 $ 24,064,000  
Loan maturity date Jan. 01, 2031     Jan. 01, 2031    
Mortgage loan $ 72,000,000     $ 72,000,000    
Gain (loss) on sale of property $ 10,400,000