Mortgages, Loans Payable And Other Obligations (Summary Of Mortgages, Loans Payable And Other Obligations) (Details)
 3 Months Ended
Apr. 22, 2016
USD ($)
Mar. 31, 2016
USD ($)
property
item
Mar. 31, 2015
USD ($)
Dec. 31, 2015
USD ($)
Debt Instrument [Line Items]        
Loan balance   $ 2,269,287,000   $ 2,145,393,000
Repayment of mortgages, loans payable and other obligations   $ 89,712,000 $ 25,228,000  
Minimum [Member]        
Debt Instrument [Line Items]        
Percentage of interest in venture   7.50%    
Maximum [Member]        
Debt Instrument [Line Items]        
Percentage of interest in venture   85.00%    
Secured Debt [Member]        
Debt Instrument [Line Items]        
Loan balance   $ 772,241,000   731,624,000
Adjustment for unamortized debt discount   (222,000)   (548,000)
Unamortized deferred financing costs   (4,446,000)   (4,465,000)
Total mortgages, loans payable and other obligations, net   $ 767,573,000   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    
Loan balance [1]     34,962,000
Loan maturity date [1]   Jan. 17, 2016    
Secured Debt [Member] | 6 Becker, 85 Livingston, 75 Livingston & 20 Waterview [Member]        
Debt Instrument [Line Items]        
Property Name   6 Becker, 85 Livingston, 75 Livingston & 20 Waterview    
Lender   Wells Fargo CMBS    
Effective rate [2]   10.26%    
Loan balance   $ 63,279,000   63,279,000
Loan maturity date [3]   Aug. 11, 2014    
Number of properties used to collateralized mortgage | property   4    
Secured Debt [Member] | 9200 Edmonston Road [Member]        
Debt Instrument [Line Items]        
Property Name   9200 Edmonston Road    
Lender   Principal Commercial Funding L.L.C.    
Effective rate [2]   9.78%    
Loan balance   $ 3,793,000   3,793,000
Loan maturity date [4]   May 01, 2015    
Secured Debt [Member] | 4 Becker [Member]        
Debt Instrument [Line Items]        
Property Name   4 Becker    
Lender   Wells Fargo CMBS    
Effective rate [2]   9.55%    
Loan balance   $ 40,478,000   40,631,000
Loan maturity date   May 11, 2016    
Secured Debt [Member] | Curtis Center [Member]        
Debt Instrument [Line Items]        
Property Name [5]   Curtis Center    
Lender [5]   CCRE & PREFG    
LIBOR [2],[5],[6]   LIBOR+5.912    
Spread over LIBOR [6]   5.912%    
Loan balance [5]   $ 64,000,000   64,000,000
Loan maturity date [5]   Oct. 09, 2016    
Percentage of interest in venture   50.00%    
Number of extension options | item   3    
Loan extension period   1 year    
Deferred financing costs amortization interest rate   1.362%    
Secured Debt [Member] | Curtis Center [Member] | Senior Loan [Member]        
Debt Instrument [Line Items]        
Effective rate   3.7311%    
Spread over LIBOR   3.29%    
Loan balance   $ 102,000,000    
Percentage of interest in venture   50.00%    
LIBOR measurement period   1 month    
Secured Debt [Member] | Curtis Center [Member] | Mezzanine Loan [Member]        
Debt Instrument [Line Items]        
Effective rate   9.937%    
Spread over LIBOR   9.50%    
Loan balance   $ 26,000,000    
Percentage of interest in venture   50.00%    
Maximum borrowing capacity   $ 48,000,000    
LIBOR measurement period   1 month    
Secured Debt [Member] | Various [Member]        
Debt Instrument [Line Items]        
Property Name [7]   Various    
Lender [7]   Prudential Insurance    
Effective rate [2],[7]   6.332%    
Loan balance [7]   $ 142,983,000   143,513,000
Loan maturity date [7]   Jan. 15, 2017    
Number of properties used to collateralized mortgage | property   7    
Repayment of mortgages, loans payable and other obligations   $ 61,100,000    
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    
Loan balance [8]   $ 16,103,000   10,937,000
Loan maturity date [8]   Mar. 30, 2017    
Secured Debt [Member] | 150 Main St [Member] | Construction Loan [Member]        
Debt Instrument [Line Items]        
Maximum borrowing capacity   $ 28,800,000    
Secured Debt [Member] | 23 Main Street [Member]        
Debt Instrument [Line Items]        
Property Name   23 Main Street    
Lender   JPMorgan CMBS    
Effective rate [2]   5.587%    
Loan balance   $ 28,367,000   28,541,000
Loan maturity date   Sep. 01, 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%    
Loan balance   $ 216,738,000   217,736,000
Loan maturity date   Nov. 01, 2018    
Secured Debt [Member] | 100 Walnut Avenue [Member]        
Debt Instrument [Line Items]        
Property Name   100 Walnut Avenue    
Lender   Guardian Life Insurance Co.    
Effective rate [2]   7.311%    
Loan balance   $ 18,202,000   18,273,000
Loan maturity date   Feb. 01, 2019    
Secured Debt [Member] | One River Center [Member]        
Debt Instrument [Line Items]        
Property Name [7]   One River Center    
Lender [7]   Guardian Life Insurance Co.    
Effective rate [2],[7]   7.311%    
Loan balance [7]   $ 41,698,000   41,859,000
Loan maturity date [7]   Feb. 01, 2019    
Number of properties used to collateralized mortgage | property   3    
Secured Debt [Member] | Park Square [Member]        
Debt Instrument [Line Items]        
Property Name   Park Square    
Lender   Wells Fargo Bank N.A.    
LIBOR [2],[9]   LIBOR+1.872    
Spread over LIBOR [9]   1.872%    
Loan balance   $ 27,500,000   27,500,000
Loan maturity date   Apr. 10, 2019    
Deferred financing costs amortization interest rate   0.122%    
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%    
Loan balance   $ 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%    
Loan balance   $ 72,500,000    
Loan maturity date   Feb. 01, 2023    
Secured Debt [Member] | Port Imperial 4/5 Garage Development [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%    
Loan balance   $ 32,600,000   $ 32,600,000
Loan maturity date   Dec. 01, 2029    
Secured Debt [Member] | Subsequent Event [Member] | 6 Becker, 85 Livingston, 75 Livingston & 20 Waterview [Member]        
Debt Instrument [Line Items]        
Repayment of mortgages, loans payable and other obligations $ 51,500,000      
[1] The loan was repaid in full at maturity, using borrowings from the Company's 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] Mortgage is cross collateralized by the four properties. On April 22, 2016, the loan was repaid for $51.5 million.
[4] Excess cash flow, as defined, is being held by the lender for re-leasing costs. The deed for the property was placed in escrow and is available to the lender in the event of default or non-payment at maturity. The mortgage loan was not repaid at maturity on May 1, 2015. The Company is in discussions with the lender regarding a further extension of the loan.
[5] The Company owns a 50 percent tenants-in-common interest in the Curtis Center property. The Company's $64.0 million loan consists of its 50 percent interest in a $102 million senior loan with a current rate of 3.7311 percent at March 31, 2016 and its 50 percent interest in a $26 million mezzanine loan (with a maximum borrowing capacity of $48 million) with a current rate of 9.937 percent at March 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. The loans provide for three one-year extension options.
[6] The effective interest rate includes amortization of deferred financing costs of 1.362 percent.
[7] Mortgage is collateralized by the three properties comprising One River Center.
[8] This construction loan has a maximum borrowing capacity of $28.8 million.
[9] The effective interest rate includes amortization of deferred financing costs of 0.122 percent.