Annual report pursuant to Section 13 and 15(d)

Investments In Unconsolidated Joint Ventures (Roseland/Port Imperial Partners, L.P.) (Narrative) (Details)

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Investments In Unconsolidated Joint Ventures (Roseland/Port Imperial Partners, L.P.) (Narrative) (Details) (USD $)
 12 Months Ended
Dec. 31, 2012
Oct. 23, 2012
item
Prudential [Member]
    
Schedule of Equity Method Investments [Line Items]    
Third party ownership percentage   79.00%
Capital balance 14,700,000  
Prudential-Port Imperial, L.L.C. [Member]
    
Schedule of Equity Method Investments [Line Items]    
Third party ownership percentage   1.00%
Roseland/Port Imperial Partners, L.P. [Member]
    
Schedule of Equity Method Investments [Line Items]    
Residual ownership interest   20.00%
Number of units   363
Percentage of operating return on capital 10.00%  
Percentage of return on additional capital contribution 10.00%  
Holding and distribution pattern under operating agreement The operating agreement of Roseland/PI provides, among other things, for the distribution of net cash flow to the members, as follows:to Prudential and Prudential LLC, in proportion to the excess of their operating return of ten percent on Prudential's Parcel C contribution, as defined, accrued to the date of such distribution over the aggregate amounts previously distributed to such partner for such return; to the partners, to the extent of any excess of such partner's operating return of ten percent on its additional capital contributions over the aggregate amounts previously distributed for such return; andto the partners in accordance with their percentage interests.  
Roseland/Port Imperial Partners, L.P. [Member] | Prudential And Prudential-Port Imperial, L.L.C. [Member]
    
Schedule of Equity Method Investments [Line Items]    
Capital balance 18,100,000  
Accumulated unpaid operating return 2,200,000  
Roseland/Port Imperial Partners, L.P. [Member] | Land [Member] | Prudential And Prudential-Port Imperial, L.L.C. [Member]
    
Schedule of Equity Method Investments [Line Items]    
Capital balance 57,700,000  
Roseland/Port Imperial Partners, L.P. [Member] | Land [Member] | Parent Company [Member]
    
Schedule of Equity Method Investments [Line Items]    
Capital balance 5,000,000