Investments In Unconsolidated Joint Ventures (Summary Of The Results Of Financial Position) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]
Rental property, net	$ 138,806	$ 143,369
Loan receivable	41,610
Other assets	75,536	71,920
Total assets	255,952	215,289
Mortgages, loans payable and other obligations	137,925	140,975
Other liabilities	8,313	6,884
Partners'/members' capital (deficit)	109,714	67,430
Total liabilities and partners'/members' capital (deficit)	255,952	215,289
Company's investments in unconsolidated joint ventures, net	65,559	32,015
Plaza VIII & IX Associates [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	7,875	8,335
Other assets	1,478	933
Total assets	9,353	9,268
Other liabilities	530	531
Partners'/members' capital (deficit)	8,823	8,737
Total liabilities and partners'/members' capital (deficit)	9,353	9,268
Company's investments in unconsolidated joint ventures, net	4,334	4,291
Harborside South Pier [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	56,265	59,733
Other assets	14,623	12,840
Total assets	70,888	72,573
Mortgages, loans payable and other obligations	69,405	70,690
Other liabilities	5,814	4,982
Partners'/members' capital (deficit)	(4,331)	(3,099)
Total liabilities and partners'/members' capital (deficit)	70,888	72,573
Company's investments in unconsolidated joint ventures, net	(960)	(343)
Red Bank Corporate Plaza [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	22,353	22,903
Other assets	3,301	2,909
Total assets	25,654	25,812
Mortgages, loans payable and other obligations	17,542	18,100
Other liabilities	309	117
Partners'/members' capital (deficit)	7,803	7,595
Total liabilities and partners'/members' capital (deficit)	25,654	25,812
Company's investments in unconsolidated joint ventures, net	3,804	3,676
Gramercy Agreement [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	38,267	39,276
Other assets	5,680	5,669
Total assets	43,947	44,945
Mortgages, loans payable and other obligations	50,978	50,978
Other liabilities	935	1,086
Partners'/members' capital (deficit)	(7,966)	(7,119)
Total liabilities and partners'/members' capital (deficit)	43,947	44,945
12 Vreeland [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	14,046	13,122
Other assets	1,356	521
Total assets	15,402	13,643
Mortgages, loans payable and other obligations		1,207
Other liabilities	725	168
Partners'/members' capital (deficit)	14,677	12,268
Total liabilities and partners'/members' capital (deficit)	15,402	13,643
Company's investments in unconsolidated joint ventures, net	10,837	10,233
Boston-Downtown Crossing [Member]
Schedule of Equity Method Investments [Line Items]
Other assets	46,198	46,121
Total assets	46,198	46,121
Partners'/members' capital (deficit)	46,198	46,121
Total liabilities and partners'/members' capital (deficit)	46,198	46,121
Company's investments in unconsolidated joint ventures, net	13,006	13,005
Gale Jefferson [Member]
Schedule of Equity Method Investments [Line Items]
Other assets	2,673	2,927
Total assets	2,673	2,927
Partners'/members' capital (deficit)	2,673	2,927
Total liabilities and partners'/members' capital (deficit)	2,673	2,927
Company's investments in unconsolidated joint ventures, net	1,068	1,153
Stamford SM LLC [Member]
Schedule of Equity Method Investments [Line Items]
Loan receivable	41,610
Other assets	227
Total assets	41,837
Partners'/members' capital (deficit)	41,837
Total liabilities and partners'/members' capital (deficit)	41,837
Company's investments in unconsolidated joint ventures, net	$ 33,470