Mortgages, Loans Payable And Other Obligations (Summary Of Mortgages, Loans Payable And Other Obligations) (Details)
 1 Months Ended 3 Months Ended 12 Months Ended
Dec. 22, 2016
USD ($)
Dec. 05, 2016
USD ($)
May 05, 2016
USD ($)
Apr. 22, 2016
USD ($)
Oct. 31, 2016
item
Dec. 31, 2016
USD ($)
Sep. 30, 2016
USD ($)
Jun. 30, 2016
USD ($)
Dec. 31, 2016
USD ($)
property
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Feb. 03, 2017
Jul. 31, 2016
USD ($)
Debt Instrument [Line Items]                          
Principal balance outstanding           $ 2,340,009,000     $ 2,340,009,000 $ 2,145,393,000      
Repayment of mortgages, loans payable and other obligations                 349,426,000 43,133,000 $ 83,808,000    
Adjustment for unamortized debt discount           (4,430,000)     (4,430,000)        
Loss from extinguishment of debt, net           (23,658,000) $ (19,302,000) $ 12,420,000 12,420,000    
Secured Debt           $ 888,585,000     $ 888,585,000 726,611,000      
Minimum [Member]                          
Debt Instrument [Line Items]                          
Percentage of interest in venture           7.50%     7.50%        
Maximum [Member]                          
Debt Instrument [Line Items]                          
Percentage of interest in venture           85.00%     85.00%        
6 Becker, 85 Livingston, 75 Livingston & 20 Waterview [Member]                          
Debt Instrument [Line Items]                          
Repayment of mortgages, loans payable and other obligations       $ 51,500,000                  
Loss from extinguishment of debt, net       $ 12,400,000                  
9200 Edmonston Road [Member]                          
Debt Instrument [Line Items]                          
Gain on sale     $ 200,000                    
4 Becker [Member]                          
Debt Instrument [Line Items]                          
Gain on sale   $ 10,400,000                      
100 Walnut Avenue [Member]                          
Debt Instrument [Line Items]                          
Loss from extinguishment of debt, net $ 2,300,000                        
150 Main St [Member] | Construction Loan [Member]                          
Debt Instrument [Line Items]                          
Maximum borrowing capacity           $ 28,800,000     $ 28,800,000        
Curtis Center [Member]                          
Debt Instrument [Line Items]                          
Principal balance outstanding           $ 75,000,000     $ 75,000,000        
Percentage of interest in venture           50.00%     50.00%        
Number of extension options | item         3                
Loan extension period         1 year                
Curtis Center [Member] | Senior Loan [Member]                          
Debt Instrument [Line Items]                          
Effective rate           3.998%     3.998%        
Spread over LIBOR                 3.29%        
Percentage of interest in venture           50.00%     50.00%        
LIBOR measurement period                 1 month        
Secured Debt           $ 102,000,000     $ 102,000,000        
Curtis Center [Member] | Mezzanine Loan [Member]                          
Debt Instrument [Line Items]                          
Effective rate           10.204%     10.204%        
Spread over LIBOR                 9.50%        
Principal balance outstanding           $ 48,000,000     $ 48,000,000        
Percentage of interest in venture           50.00%     50.00%        
LIBOR measurement period                 1 month        
Port Imperial 4/5 Hotel [Member] | Construction Loan [Member]                          
Debt Instrument [Line Items]                          
Maximum borrowing capacity           $ 94,000,000     $ 94,000,000        
Chase II Project [Member] | Construction Loan [Member]                          
Debt Instrument [Line Items]                          
Maximum borrowing capacity           48,000,000     $ 48,000,000        
One River Center [Member]                          
Debt Instrument [Line Items]                          
Number of properties used to collateralized mortgage | property                 3        
Park Square [Member]                          
Debt Instrument [Line Items]                          
Deferred financing costs amortization interest rate                 0.122%        
Port Imperial South 11 [Member] | Construction Loan [Member]                          
Debt Instrument [Line Items]                          
Maximum borrowing capacity           78,000,000     $ 78,000,000        
Portside 7 [Member]                          
Debt Instrument [Line Items]                          
Principal balance outstanding                         $ 42,500,000
101 Hudson Street [Member] | Construction Loan [Member]                          
Debt Instrument [Line Items]                          
Deferred financing costs amortization interest rate                 0.0798%        
Subsequent Event [Member]                          
Debt Instrument [Line Items]                          
Percentage of interest in venture                       100.00%  
Secured Debt [Member]                          
Debt Instrument [Line Items]                          
Principal balance outstanding           896,055,000     $ 896,055,000 731,624,000      
Adjustment for unamortized debt discount               (548,000)      
Unamortized deferred financing costs           (7,470,000)     (7,470,000) (4,465,000)      
Total mortgages, loans payable and other obligations, net           888,585,000     $ 888,585,000 726,611,000      
Secured Debt [Member] | Port Imperial South [Member]                          
Debt Instrument [Line Items]                          
Property Name [1]                 Port Imperial South        
Lender [1]                 Wells Fargo Bank N.A.        
LIBOR [1],[2]                 LIBOR+1.75        
Spread over LIBOR                 1.75%        
Principal balance outstanding [1]               34,962,000      
Secured Debt [Member] | 6 Becker, 85 Livingston, 75 Livingston & 20 Waterview [Member]                          
Debt Instrument [Line Items]                          
Property Name [3]                 6 Becker, 85 Livingston, 75 Livingston & 20 Waterview        
Lender [3]                 Wells Fargo CMBS        
Effective rate [2],[3]           10.26%     10.26%        
Principal balance outstanding [3]               63,279,000      
Secured Debt [Member] | 9200 Edmonston Road [Member]                          
Debt Instrument [Line Items]                          
Property Name [4]                 9200 Edmonston Road        
Lender [4]                 Principal Commercial Funding L.L.C.        
Effective rate [2],[4]           9.78%     9.78%        
Principal balance outstanding [4]               3,793,000      
Secured Debt [Member] | Various [Member]                          
Debt Instrument [Line Items]                          
Property Name [5]                 Various        
Lender [5]                 Prudential Insurance        
Effective rate [2],[5]           6.332%     6.332%        
Principal balance outstanding [5]               143,513,000      
Secured Debt [Member] | 4 Becker [Member]                          
Debt Instrument [Line Items]                          
Property Name [6]                 4 Becker        
Lender [6]                 Wells Fargo CMBS        
Effective rate [2],[6]           11.26%     11.26%        
Principal balance outstanding [6]               40,631,000      
Secured Debt [Member] | 100 Walnut Avenue [Member]                          
Debt Instrument [Line Items]                          
Property Name [7]                 100 Walnut Avenue        
Lender [7]                 Guardian Life Insurance Co.        
Effective rate [2],[7]           7.311%     7.311%        
Principal balance outstanding [7]               18,273,000      
Secured Debt [Member] | 150 Main St [Member]                          
Debt Instrument [Line Items]                          
Property Name [8]                 150 Main St.        
Lender [8]                 Webster Bank        
LIBOR [2],[8]                 LIBOR+2.35        
Spread over LIBOR                 2.35%        
Principal balance outstanding [8]           26,642,000     $ 26,642,000 10,937,000      
Loan maturity date [8]                 Mar. 30, 2017        
Secured Debt [Member] | Curtis Center [Member]                          
Debt Instrument [Line Items]                          
Property Name [9]                 Curtis Center        
Lender [9]                 CCRE & PREFG        
LIBOR [2],[9]                 LIBOR+5.912        
Spread over LIBOR                 5.912%        
Principal balance outstanding [9]           $ 75,000,000     $ 75,000,000 64,000,000      
Loan maturity date [9]                 Oct. 09, 2017        
Secured Debt [Member] | 23 Main Street [Member]                          
Debt Instrument [Line Items]                          
Property Name                 23 Main Street        
Lender                 JPMorgan CMBS        
Effective rate [2]           5.587%     5.587%        
Principal balance outstanding           $ 27,838,000     $ 27,838,000 28,541,000      
Loan maturity date                 Sep. 01, 2018        
Secured Debt [Member] | Port Imperial 4/5 Hotel [Member]                          
Debt Instrument [Line Items]                          
Property Name [10]                 Port Imperial 4/5 Hotel        
Lender [10]                 Fifth Third Bank & Santander        
LIBOR [2],[10]                 LIBOR+4.50        
Spread over LIBOR                 4.50%        
Principal balance outstanding [10]           $ 14,919,000     $ 14,919,000        
Loan maturity date [10]                 Oct. 06, 2018        
Secured Debt [Member] | Harborside Plaza 5 [Member]                          
Debt Instrument [Line Items]                          
Property Name                 Harborside Plaza 5        
Lender                 The Northwestern Mutual Life Insurance Co. & New York Life Insurance Co.        
Effective rate [2]           6.842%     6.842%        
Principal balance outstanding           $ 213,640,000     $ 213,640,000 217,736,000      
Loan maturity date                 Nov. 01, 2018        
Secured Debt [Member] | Chase II Project [Member]                          
Debt Instrument [Line Items]                          
Property Name [11]                 Chase II        
Lender [11]                 Fifth Third Bank        
LIBOR [2],[11]                 LIBOR+2.25        
Spread over LIBOR                 2.25%        
Principal balance outstanding [11]           $ 34,708,000     $ 34,708,000        
Loan maturity date [11]                 Dec. 16, 2018        
Secured Debt [Member] | One River Center [Member]                          
Debt Instrument [Line Items]                          
Property Name [12]                 One River Center        
Lender [12]                 Guardian Life Insurance Co.        
Effective rate [2],[12]           7.311%     7.311%        
Principal balance outstanding [12]           $ 41,197,000     $ 41,197,000 41,859,000      
Loan maturity date [12]                 Feb. 01, 2019        
Secured Debt [Member] | Park Square [Member]                          
Debt Instrument [Line Items]                          
Property Name                 Park Square        
Lender                 Wells Fargo Bank N.A.        
LIBOR [2],[13]                 LIBOR+1.872        
Spread over LIBOR [13]                 1.872%        
Principal balance outstanding           27,500,000     $ 27,500,000 27,500,000      
Loan maturity date                 Apr. 10, 2019        
Secured Debt [Member] | 250 Johnson Road [Member]                          
Debt Instrument [Line Items]                          
Property Name                 250 Johnson        
Lender                 M&T Bank        
LIBOR [2]                 LIBOR+2.35        
Spread over LIBOR                 2.35%        
Principal balance outstanding           2,440,000     $ 2,440,000        
Loan maturity date                 May 20, 2019        
Secured Debt [Member] | Port Imperial South 11 [Member]                          
Debt Instrument [Line Items]                          
Property Name [14]                 Port Imperial South 11        
Lender [14]                 JPMorgan Chase        
LIBOR [2],[14]                 LIBOR+2.35        
Spread over LIBOR                 2.35%        
Principal balance outstanding [14]           $ 14,073,000     $ 14,073,000        
Loan maturity date [14]                 Nov. 24, 2019        
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 [2]           4.559%     4.559%        
Principal balance outstanding           $ 4,000,000     $ 4,000,000 4,000,000      
Loan maturity date                 Dec. 01, 2021        
Secured Debt [Member] | The Chase At Overlook Ridge [Member]                          
Debt Instrument [Line Items]                          
Property Name                 The Chase at Overlook Ridge        
Lender                 New York Community Bank        
Effective rate [2]           3.74%     3.74%        
Principal balance outstanding           $ 72,500,000     $ 72,500,000        
Loan maturity date                 Feb. 01, 2023        
Secured Debt [Member] | Portside 7 [Member]                          
Debt Instrument [Line Items]                          
Property Name [15]                 Portside 7        
Lender [15]                 CBRE Capital Markets/FreddieMac        
Effective rate [2],[15]           3.569%     3.569%        
Principal balance outstanding [15]           $ 58,998,000     $ 58,998,000        
Loan maturity date [15]                 Aug. 01, 2023        
Secured Debt [Member] | 101 Hudson Street [Member]                          
Debt Instrument [Line Items]                          
Property Name [16]                 101 Hudson        
Lender [16]                 Wells Fargo CMBS        
Effective rate [2],[16],[17]           3.197%     3.197%        
Principal balance outstanding [16]           $ 250,000,000     $ 250,000,000        
Loan maturity date [16]                 Oct. 11, 2026        
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 [2]           4.853%     4.853%        
Principal balance outstanding           $ 32,600,000     $ 32,600,000 $ 32,600,000      
Loan maturity date                 Dec. 01, 2029        
[1] On January 19, 2016, the loan was repaid in full at maturity, using borrowings from the Company's unsecured revolving credit facility.
[2] Reflects effective rate of debt, including deferred financing costs, comprised of the cost of terminated treasury lock agreements (if any), debt initiation costs, mark-to-market adjustment of acquired debt and other transaction costs, as applicable.
[3] On April 22, 2016, the loan was repaid at a discount for $51.5 million, using borrowings from the Company's unsecured revolving credit facility. Accordingly, the Company recognized a gain on extinguishment of debt of $12.4 million, which is included in loss on extinguishment of debt, net.
[4] On May 5, 2016, the Company transferred the deed for 9200 Edmonston Road to the lender in satisfaction of its obligations and recorded a gain of $0.2 million.
[5] On November 16, 2016, the loan was repaid in full, using borrowings from the Company's unsecured revolving credit facility.
[6] On December 5, 2016, the Company transferred the deed for 4 Becker Farm Road to the lender in satisfaction of its obligations and recorded a gain of $10.4 million.
[7] On December 22, 2016, the loan was repaid at a premium, using proceeds from the disposition of 100 Walnut Avenue. Accordingly, the Company recognized a loss on extinguishment of debt of $2.3 million, which is included in loss on extinguishment of debt, net.
[8] This construction loan has a maximum borrowing capacity of $28.8 million.
[9] The Company owns a 50 percent tenants-in-common interest in the Curtis Center property. The Company's $75 million loan consists of its 50 percent interest in a $102 million senior loan with a current rate of 3.998 percent at December 31, 2016 and its 50 percent interest in a $48 million mezzanine loan with a current rate of 10.204 percent at December 31, 2016. The senior loan rate is based on a floating rate of one-month LIBOR plus 329 basis points and the mezzanine loan rate is based on a floating rate of one-month LIBOR plus 950 basis points. The Company has entered into LIBOR caps for the periods of the loans. In October 2016, the first of three one-year extension options was exercised by the venture.
[10] This construction loan has a maximum borrowing capacity of $94 million.
[11] This construction loan has a maximum borrowing capacity of $48 million.
[12] Mortgage is collateralized by the three properties comprising One River Center.
[13] The effective interest rate includes amortization of deferred financing costs of 0.122 percent.
[14] This constuction loan has a maximum borrowing capacity of $78 million.
[15] This mortgage loan was obtained by the Company in July 2016 to replace a $42.5 million mortgage loan that was in place at the property acquisition date of April 1, 2016.
[16] This mortgage loan was obtained by the Company on September 30, 2016.
[17] The effective interest rate includes amortization of deferred financing costs of 0.0798 percent.