Investments In Unconsolidated Joint Ventures (Summary Of Company's Investment In Unconsolidated Joint Ventures) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	$ 158,505	$ 132,339
Plaza VIII & IX Associates, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	4,022	4,321
South Pier At Harborside [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	(2,487)	(1,225)
Red Bank Corporate Plaza, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	3,985	3,876
12 Vreeland Associates, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	12,748	12,840
Boston Downtown Crossing [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	13,012	13,012
Gale Jefferson, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures		1,029
Stamford SM LLC [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	34,547	34,006
Marbella RoseGarden, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	16,601	16,918
RoseGarden Monaco Holdings, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	4,363	4,761
Rosewood Lafayette Holdings, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	1,698	1,988
PruRose Port Imperial South 15, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures		606
Rosewood Morristown, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	6,935	7,091
Overlook Ridge, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	71	31
Overlook Ridge JV 2C/3B, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	91	179
Roseland/North Retail, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	2,112	2,161
BNES Associates III [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	1,839	1,955
Portside Master Company, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	3,637	3,651
PruRose Port Imperial South 13, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	2,817	2,920
Roseland/Port Imperial Partners, L.P. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	2,635	2,582
RoseGarden Marbella South, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	6,241	6,182
PruRose Riverwalk G, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	3,959	4,136
Elmajo Urban Renewal Associates, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	725	849
Riverpark At Harrison I, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	2,641	2,606
150 Main Street, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	2,602	2,395
RoseGarden Monaco, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	1,178	1,165
Hillsborough 206 Holdings, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	1,973	1,967
Grand Jersey Waterfront Urban Renewal Associates, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	337	337
Crystal House Apartments Investors LLC [Member]
Schedule of Equity Method Investments [Line Items]
Company's investments in unconsolidated joint ventures	$ 30,223