| Investments In Unconsolidated Joint Ventures (Tables)
 | 9 Months Ended | 
      
        | Sep. 30, 2013 | 
      
        | Investments In Unconsolidated Joint Ventures [Abstract] |  | 
      
        | Summary Of Financial Position Of Unconsolidated Joint Ventures |  
		
			
				| 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						  | 
						  | 
						  | 
						September 30, | 
						  | 
						  | 
						December 31, |  
				| 
						  | 
						  | 
						  | 2013 | 
						  | 
						  | 2012 |  
				| 
						Assets: | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						   Rental property, net | 
						  | 
						$ | 736,487 | 
						  | 
						$ | 180,254 |  
				| 
						   Loan receivable | 
						  | 
						  | 44,459 | 
						  | 
						  | 42,276 |  
				| 
						   Other assets | 
						  | 
						  | 434,714 | 
						  | 
						  | 311,847 |  
				| 
						   Total assets | 
						  | 
						$ | 1,215,660 | 
						  | 
						$ | 534,377 |  
				| 
						Liabilities and partners'/ | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						members' capital: | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						   Mortgages and loans payable | 
						  | 
						$ | 600,473 | 
						  | 
						$ | 168,908 |  
				| 
						   Other liabilities | 
						  | 
						  | 71,552 | 
						  | 
						  | 12,141 |  
				| 
						   Partners'/members' capital | 
						  | 
						  | 543,635 | 
						  | 
						  | 353,328 |  
				| 
						   Total liabilities and | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						   partners'/members' capital | 
						  | 
						$ | 1,215,660 | 
						  | 
						$ | 534,377 | 
			 
		   | 
      
        | Summary Of Company's Investment In Unconsolidated Joint Ventures |  
		
			
				| 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						  | 
						  | 
						September 30, | 
						  | 
						  | 
						December 31, |  
				| 
						Entity | 
						  | 2013 | 
						  | 
						  | 2012 |  
				| 
						Plaza VIII & IX Associates, L.L.C. | 
						$ | 4,065 | 
						  | 
						$ | 4,321 |  
				| 
						South Pier at Harborside | 
						  | (2,095) | 
						  | 
						  | (1,225) |  
				| 
						Red Bank Corporate Plaza, L.L.C. | 
						  | 3,972 | 
						  | 
						  | 3,876 |  
				| 
						12 Vreeland Associates, L.L.C. | 
						  | 5,439 | 
						  | 
						  | 12,840 |  
				| 
						Boston Downtown Crossing | 
						  | 
						  - | 
						  | 
						  | 13,012 |  
				| 
						Gale Jefferson, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 1,029 |  
				| 
						Stamford SM LLC | 
						  | 35,667 | 
						  | 
						  | 34,006 |  
				| 
						Marbella RoseGarden, L.L.C. | 
						  | 15,976 | 
						  | 
						  | 16,918 |  
				| 
						RoseGarden Monaco Holdings, L.L.C. | 
						  | 3,524 | 
						  | 
						  | 4,761 |  
				| 
						Rosewood Lafayette Holdings, L.L.C. | 
						  | 1,119 | 
						  | 
						  | 1,988 |  
				| 
						PruRose Port Imperial South 15, LLC | 
						  | 
						  - | 
						  | 
						  | 606 |  
				| 
						Rosewood Morristown, L.L.C. | 
						  | 6,603 | 
						  | 
						  | 7,091 |  
				| 
						Overlook Ridge JV, L.L.C. | 
						  | 178 | 
						  | 
						  | 31 |  
				| 
						Overlook Ridge, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 
						  - |  
				| 
						Overlook Ridge JV 2C/3B, L.L.C.  | 
						  | 
						  - | 
						  | 
						  | 179 |  
				| 
						Roseland/North Retail, L.L.C. | 
						  | 1,967 | 
						  | 
						  | 2,161 |  
				| 
						BNES Associates III | 
						  | 1,708 | 
						  | 
						  | 1,955 |  
				| 
						Portside Master Company, L.L.C. | 
						  | 3,449 | 
						  | 
						  | 3,651 |  
				| 
						PruRose Port Imperial South 13, LLC | 
						  | 2,451 | 
						  | 
						  | 2,920 |  
				| 
						Roseland/Port Imperial Partners, L.P. | 
						  | 2,755 | 
						  | 
						  | 2,582 |  
				| 
						RoseGarden Marbella South, L.L.C. | 
						  | 7,160 | 
						  | 
						  | 6,182 |  
				| 
						PruRose Riverwalk G, L.L.C. | 
						  | 3,515 | 
						  | 
						  | 4,136 |  
				| 
						Elmajo Urban Renewal Associates, LLC | 
						  | 232 | 
						  | 
						  | 629 |  
				| 
						Estuary Urban Renewal Unit B, LLC | 
						  | 74 | 
						  | 
						  | 220 |  
				| 
						RiverPark at Harrison I, L.L.C. | 
						  | 3,404 | 
						  | 
						  | 2,606 |  
				| 
						150 Main Street, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 2,395 |  
				| 
						RoseGarden Monaco, L.L.C. | 
						  | 1,208 | 
						  | 
						  | 1,165 |  
				| 
						Hillsborough 206 Holdings, L.L.C. | 
						  | 1,989 | 
						  | 
						  | 1,967 |  
				| 
						Grand Jersey Waterfront Urban Renewal Associates, L.L.C. | 
						  | 397 | 
						  | 
						  | 337 |  
				| 
						Crystal House Apartments Investors LLC | 
						  | 26,928 | 
						  | 
						  | 
						  - |  
				| 
						Other | 
						  | 174 | 
						  | 
						  | 
						  - |  
				| 
						Company's investment in unconsolidated joint ventures | 
						$ | 131,859 | 
						  | 
						$ | 132,339 | 
			 
		   | 
      
        | Summary Of Results Of Operations Of Unconsolidated Joint Ventures |  
		
			
				| 
						  | 
						  | 
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						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						  | 
						  | 
						               Three Months Ended | 
						  | 
						  | 
						               Nine Months Ended |  
				| 
						  | 
						  | 
						               September 30, | 
						  | 
						  | 
						               September 30, |  
				| 
						  | 
						  | 2013 | 
						  | 
						  | 2012 | 
						  | 
						  | 2013 | 
						  | 
						  | 2012 |  
				| 
						Total revenues | 
						$ | 99,117 | 
						  | 
						$ | 17,311 | 
						  | 
						$ | 202,810 | 
						  | 
						$ | 44,369 |  
				| 
						Operating and other expenses | 
						  | (48,621) | 
						  | 
						  | (9,169) | 
						  | 
						  | (137,889) | 
						  | 
						  | (25,428) |  
				| 
						Depreciation and amortization | 
						  | (11,556) | 
						  | 
						  | (2,497) | 
						  | 
						  | (24,730) | 
						  | 
						  | (7,285) |  
				| 
						Interest expense | 
						  | (3,934) | 
						  | 
						  | (1,675) | 
						  | 
						  | (9,256) | 
						  | 
						  | (5,017) |  
				| 
						Net income | 
						$ | 35,006 | 
						  | 
						$ | 3,970 | 
						  | 
						$ | 30,935 | 
						  | 
						$ | 6,639 | 
			 
		   | 
      
        | Summary Of Company's Equity In Earnings (Loss) Of Unconsolidated Joint Ventures |  
		
			
				| 
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						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						  | 
						  | 
						                 Three Months Ended | 
						  | 
						  | 
						                 Nine Months Ended |  
				| 
						  | 
						  | 
						               September 30, | 
						  | 
						  | 
						               September 30, |  
				| 
						Entity | 
						  | 2013 | 
						  | 
						  | 2012 | 
						  | 
						  | 2013 | 
						  | 
						  | 2012 |  
				| 
						Plaza VIII & IX Associates, L.L.C. | 
						$ | 24 | 
						  | 
						$ | 21 | 
						  | 
						$ | 52 | 
						  | 
						$ | 43 |  
				| 
						South Pier at Harborside | 
						  | 835 | 
						  | 
						  | 1,080 | 
						  | 
						  | 1,380 | 
						  | 
						  | 1,884 |  
				| 
						Red Bank Corporate Plaza, L.L.C. | 
						  | 99 | 
						  | 
						  | 94 | 
						  | 
						  | 306 | 
						  | 
						  | 298 |  
				| 
						12 Vreeland Associates, L.L.C. | 
						  | (25) | 
						  | 
						  | 279 | 
						  | 
						  | (1) | 
						  | 
						  | 603 |  
				| 
						Boston Downtown Crossing | 
						  | 
						  - | 
						  | 
						  | (6) | 
						  | 
						  | 646 | 
						  | 
						  | (333) |  
				| 
						Gale Jefferson, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 23 | 
						  | 
						  | 68 | 
						  | 
						  | 63 |  
				| 
						Stamford SM LLC | 
						  | 1,023 | 
						  | 
						  | 927 | 
						  | 
						  | 2,805 | 
						  | 
						  | 2,193 |  
				| 
						Marbella RoseGarden, L.L.C. | 
						  | (170) | 
						  | 
						  | 
						  - | 
						  | 
						  | (446) | 
						  | 
						  | 
						  - |  
				| 
						RoseGarden Monaco Holdings, L.L.C. | 
						  | (416) | 
						  | 
						  | 
						  - | 
						  | 
						  | (1,238) | 
						  | 
						  | 
						  - |  
				| 
						Rosewood Lafayette Holdings, L.L.C. | 
						  | (295) | 
						  | 
						  | 
						  - | 
						  | 
						  | (869) | 
						  | 
						  | 
						  - |  
				| 
						PruRose Port Imperial South 15, LLC | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | (606) | 
						  | 
						  | 
						  - |  
				| 
						Rosewood Morristown, L.L.C. | 
						  | (152) | 
						  | 
						  | 
						  - | 
						  | 
						  | (393) | 
						  | 
						  | 
						  - |  
				| 
						Overlook Ridge JV, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - |  
				| 
						Overlook Ridge, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - |  
				| 
						Overlook Ridge JV 2C/3B, L.L.C. | 
						  | 53 | 
						  | 
						  | 
						  - | 
						  | 
						  | 204 | 
						  | 
						  | 
						  - |  
				| 
						Roseland/North Retail, L.L.C. | 
						  | (62) | 
						  | 
						  | 
						  - | 
						  | 
						  | (194) | 
						  | 
						  | 
						  - |  
				| 
						BNES Associates III | 
						  | (37) | 
						  | 
						  | 
						  - | 
						  | 
						  | (108) | 
						  | 
						  | 
						  - |  
				| 
						Portside Master Company, L.L.C. | 
						  | (109) | 
						  | 
						  | 
						  - | 
						  | 
						  | (222) | 
						  | 
						  | 
						  - |  
				| 
						PruRose Port Imperial South 13, LLC | 
						  | (181) | 
						  | 
						  | 
						  - | 
						  | 
						  | (459) | 
						  | 
						  | 
						  - |  
				| 
						Roseland/Port Imperial Partners, L.P. | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - |  
				| 
						RoseGarden Marbella South, L.L.C. | 
						  | (20) | 
						  | 
						  | 
						  - | 
						  | 
						  | (57) | 
						  | 
						  | 
						  - |  
				| 
						PruRose Riverwalk G, L.L.C. | 
						  | (198) | 
						  | 
						  | 
						  - | 
						  | 
						  | (576) | 
						  | 
						  | 
						  - |  
				| 
						Elmajo Urban Renewal Associates, LLC | 
						  | (87) | 
						  | 
						  | 
						  - | 
						  | 
						  | (255) | 
						  | 
						  | 
						  - |  
				| 
						Estuary Urban Renewal Unit B, LLC | 
						  | (44) | 
						  | 
						  | 
						  - | 
						  | 
						  | (107) | 
						  | 
						  | 
						  - |  
				| 
						RiverPark at Harrison I, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - |  
				| 
						150 Main Street, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - |  
				| 
						RoseGarden Monaco, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - |  
				| 
						Hillsborough 206 Holdings, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - |  
				| 
						Grand Jersey Waterfront Urban Renewal Associates, L.L.C. | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - | 
						  | 
						  | 
						  - |  
				| 
						Crystal House Apartments Investors LLC | 
						  | (1,149) | 
						  | 
						  | 
						  - | 
						  | 
						  | (2,671) | 
						  | 
						  | 
						  - |  
				| 
						Other | 
						  | 682 | 
						  | 
						  | 
						  | 
						  | 
						  | 682 | 
						  | 
						  | 
						  |  
				| 
						Company's equity in earnings of unconsolidated joint ventures | 
						$ | (229) | 
						  | 
						$ | 2,418 | 
						  | 
						$ | (2,059) | 
						  | 
						$ | 4,751 | 
			 
		   |