Annual report pursuant to Section 13 and 15(d)

Investments In Unconsolidated Joint Ventures (Summary Of Company's Equity In Earnings (Loss) Of Unconsolidated Joint Ventures) (Details)

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Investments In Unconsolidated Joint Ventures (Summary Of Company's Equity In Earnings (Loss) Of Unconsolidated Joint Ventures) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2011
Sep. 30, 2011
Jun. 30, 2011
Mar. 31, 2011
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures $ (662) $ 2,418 $ 1,733 $ 600 $ 848 $ 539 $ 736 $ (101) $ 4,089 [1] $ 2,022 [1] $ 2,276 [1]
Plaza VIII & IX Associates, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 30 68 (10)
South Pier At Harborside [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 2,368 1,495 301
Red Bank Corporate Plaza, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 360 446 649
12 Vreeland Associates, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 427 374 260
Gale Kimball [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                     1,909
Princeton Forrestal Village [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                     (379)
Boston Downtown Crossing [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (458) (448) (437)
Gale Jefferson, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 81 87 (17)
Stamford SM LLC [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 3,078    
Marbella RoseGarden, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 13    
RoseGarden Monaco Holdings, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (311)    
Rosewood Lafayette Holdings, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (197)    
PruRose Port Imperial South 15, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (533)    
Rosewood Morristown, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (25)    
Overlook Ridge JV 2C/3B, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (11)    
Roseland/North Retail, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (80)    
BNES Associates III [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (323)    
Portside Master Company, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (5)    
PruRose Port Imperial South 13, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (87)    
RoseGarden Marbella South, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (13)    
PruRose Riverwalk G, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 (142)    
Elmajo Urban Renewal Associates, L.L.C. [Member]
                      
Schedule of Equity Method Investments [Line Items]                      
Company's equity in earnings of unconsolidated joint ventures                 $ (83)    
[1] Included in the real estate segment for these items are the effects of the Roseland Assets acquired in 2012.