| Investments In Unconsolidated Joint Ventures (Tables)
 | 12 Months Ended | 
      
        | Dec. 31, 2012 | 
      
        | Investments In Unconsolidated Joint Ventures [Abstract] |  | 
      
        | Summary Of Financial Position Of Unconsolidated Joint Ventures |  
		
			
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						         December 31, |  
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						  | 
						  | 
						  | 2012 | 
						  | 
						  | 2011 |  
				| 
						Assets: | 
						  | 
						  | 
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				| 
						   Rental property, net | 
						  | 
						$ | 179,824 | 
						  | 
						$ | 143,369 |  
				| 
						   Loan receivable | 
						  | 
						  | 42,276 | 
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						  | 
						  - |  
				| 
						   Other assets | 
						  | 
						  | 311,846 | 
						  | 
						  | 71,928 |  
				| 
						   Total assets | 
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						$ | 533,946 | 
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						$ | 215,297 |  
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						Liabilities and partners'/ | 
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						members' capital: | 
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						   Mortgages and loans payable | 
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						$ | 168,908 | 
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						$ | 140,975 |  
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						   Other liabilities | 
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						  | 12,203 | 
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						  | 6,884 |  
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						   Partners'/members' capital | 
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						  | 352,835 | 
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						  | 67,438 |  
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						   Total liabilities and | 
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						   partners'/members' capital | 
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						$ | 533,946 | 
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						$ | 215,297 | 
			 
		   | 
      
        | Summary Of Company's Investment In Unconsolidated Joint Ventures |  
		
			
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						 December 31,  |  
				| 
						Entity | 
						  | 2012 | 
						  | 
						  | 2011 |  
				| 
						Plaza VIII & IX Associates, L.L.C. | 
						$ | 4,321 | 
						  | 
						$ | 4,291 |  
				| 
						South Pier at Harborside | 
						  | (1,225) | 
						  | 
						  | (343) |  
				| 
						Red Bank Corporate Plaza, L.L.C. | 
						  | 3,876 | 
						  | 
						  | 3,676 |  
				| 
						12 Vreeland Associates, L.L.C. | 
						  | 12,840 | 
						  | 
						  | 10,233 |  
				| 
						Boston Downtown Crossing | 
						  | 13,012 | 
						  | 
						  | 13,005 |  
				| 
						Gale Jefferson L.L.C. | 
						  | 1,029 | 
						  | 
						  | 1,153 |  
				| 
						Stamford SM LLC | 
						  | 34,006 | 
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						  | 
						  - |  
				| 
						Marbella RoseGarden, L.L.C. | 
						  | 16,918 | 
						  | 
						  | 
						  - |  
				| 
						RoseGarden Monaco Holdings, L.L.C. | 
						  | 4,761 | 
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						  - |  
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						Rosewood Lafayette Holdings, L.L.C. | 
						  | 1,988 | 
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						  - |  
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						PruRose Port Imperial South 15, LLC | 
						  | 606 | 
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						  - |  
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						Rosewood Morristown, L.L.C. | 
						  | 7,091 | 
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						  - |  
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						Overlook Ridge JV, L.L.C. | 
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						  - | 
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						  - |  
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						Overlook Ridge, L.L.C. | 
						  | 31 | 
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						  - |  
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						Overlook Ridge JV 2C/3B, L.L.C.  | 
						  | 179 | 
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						  - |  
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						Roseland/North Retail, L.L.C. | 
						  | 2,161 | 
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						  - |  
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						BNES Associates III | 
						  | 1,955 | 
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						  - |  
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						Portside Master Company, L.L.C. | 
						  | 3,651 | 
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						  - |  
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						PruRose Port Imperial South 13, LLC | 
						  | 2,920 | 
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						  - |  
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						Roseland/Port Imperial Partners, L.P. | 
						  | 2,582 | 
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						  - |  
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						RoseGarden Marbella South, L.L.C. | 
						  | 6,182 | 
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						  - |  
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						PruRose Riverwalk G, L.L.C. | 
						  | 4,136 | 
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						  - |  
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						Elmajo Urban Renewal Associates, LLC | 
						  | 849 | 
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						  - |  
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						Riverpark at Harrison I, L.L.C. | 
						  | 2,606 | 
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						  - |  
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						150 Main Street, L.L.C. | 
						  | 2,395 | 
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						  - |  
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						RoseGarden Monaco, L.L.C. | 
						  | 1,165 | 
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						  - |  
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						Hillsborough 206 Holdings, L.L.C. | 
						  | 1,967 | 
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						  - |  
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						Grand Jersey Waterfront Urban Renewal Associates, L.L.C. | 
						  | 337 | 
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						  - |  
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						Company's investment in unconsolidated joint ventures | 
						$ | 132,339 | 
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						$ | 32,015 | 
			 
		   | 
      
        | Summary Of Results Of Operations Of Unconsolidated Joint Ventures |  
		
			
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						Year Ended December 31, |  
				| 
						  | 
						  | 2012 | 
						  | 
						  | 2011 | 
						  | 
						  | 2010 |  
				| 
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						Total revenues | 
						$ | 68,183 | 
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						$ | 51,308 | 
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						$ | 76,862 |  
				| 
						Operating and other expenses | 
						  | (37,008) | 
						  | 
						  | (32,074) | 
						  | 
						  | (39,542) |  
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						Depreciation and amortization | 
						  | (10,139) | 
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						  | (10,593) | 
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						  | (15,110) |  
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						Interest expense | 
						  | (6,775) | 
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						  | (6,743) | 
						  | 
						  | (9,182) |  
				| 
						Net income | 
						$ | 14,261 | 
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						$ | 1,898 | 
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						$ | 13,028 | 
			 
		   | 
      
        | Summary Of Company's Equity In Earnings (Loss) Of Unconsolidated Joint Ventures |  
		
			
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						Year Ended December 31, |  
				| 
						Entity | 
						  | 2012 | 
						  | 
						  | 2011 | 
						  | 
						  | 2010 |  
				| 
						Plaza VIII & IX Associates, L.L.C. | 
						$ | 30 | 
						  | 
						$ | 68 | 
						  | 
						$ | (10) |  
				| 
						South Pier at Harborside | 
						  | 2,368 | 
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						  | 1,495 | 
						  | 
						  | 301 |  
				| 
						Red Bank Corporate Plaza, L.L.C. | 
						  | 360 | 
						  | 
						  | 446 | 
						  | 
						  | 649 |  
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						12 Vreeland Associates, L.L.C. | 
						  | 427 | 
						  | 
						  | 374 | 
						  | 
						  | 260 |  
				| 
						Gale Kimball | 
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						  - | 
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						  - | 
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						  | 1,909 |  
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						Princeton Forrestal Village | 
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						  - | 
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						  - | 
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						  | (379) |  
				| 
						Boston Downtown Crossing | 
						  | (458) | 
						  | 
						  | (448) | 
						  | 
						  | (437) |  
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						Gale Jefferson L.L.C. | 
						  | 81 | 
						  | 
						  | 87 | 
						  | 
						  | (17) |  
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						Stamford SM LLC | 
						  | 3,078 | 
						  | 
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						  - | 
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						  - |  
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						Marbella RoseGarden, L.L.C. | 
						  | 13 | 
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						  - | 
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						  - |  
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						RoseGarden Monaco Holdings, L.L.C. | 
						  | (311) | 
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						  - | 
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						  - |  
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						Rosewood Lafayette Holdings, L.L.C. | 
						  | (197) | 
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						  - | 
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						  - |  
				| 
						PruRose Port Imperial South 15, LLC | 
						  | (533) | 
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						  - | 
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						  - |  
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						Rosewood Morristown, L.L.C. | 
						  | (25) | 
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						  - | 
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						  - |  
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						Overlook Ridge JV, L.L.C. | 
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						  - | 
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						  - | 
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						  - |  
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						Overlook Ridge, L.L.C. | 
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						  - | 
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						  - | 
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						  - |  
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						Overlook Ridge JV 2C/3B, L.L.C. | 
						  | (11) | 
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						  - | 
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						  - |  
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						Roseland/North Retail, L.L.C. | 
						  | (80) | 
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						  - | 
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						  - |  
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						BNES Associates III | 
						  | (323) | 
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						  | 
						  - | 
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						  - |  
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						Portside Master Company, L.L.C. | 
						  | (5) | 
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						  - | 
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						  - |  
				| 
						PruRose Port Imperial South 13, LLC | 
						  | (87) | 
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						  - | 
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						  - |  
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						Roseland/Port Imperial Partners, L.P. | 
						  | 
						  - | 
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						  - | 
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						  - |  
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						RoseGarden Marbella South, L.L.C. | 
						  | (13) | 
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						  - | 
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						  - |  
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						PruRose Riverwalk G, L.L.C. | 
						  | (142) | 
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						  - | 
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						  - |  
				| 
						Elmajo Urban Renewal Associates, LLC | 
						  | (83) | 
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						  - | 
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						  - |  
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						Riverpark at Harrison I, L.L.C. | 
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						  - | 
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						  - | 
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						  - |  
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						150 Main Street, L.L.C. | 
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						  - | 
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						  - | 
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						  - |  
				| 
						RoseGarden Monaco, L.L.C. | 
						  | 
						  - | 
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						  - | 
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						  - |  
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						Hillsborough 206 Holdings, L.L.C. | 
						  | 
						  - | 
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						  - | 
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						  - |  
				| 
						Grand Jersey Waterfront Urban Renewal Associates, L.L.C. | 
						  | 
						  - | 
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						  - | 
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						  - |  
				| 
						Company's equity in earnings of unconsolidated joint ventures | 
						$ | 4,089 | 
						  | 
						$ | 2,022 | 
						  | 
						$ | 2,276 | 
			 
		   |