Investments In Unconsolidated Joint Ventures (Summary Of The Results Of Financial Position) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]
Rental property, net	$ 142,588	$ 143,369
Other assets	113,060	71,920
Total assets	255,648	215,289
Mortgages, loans payable and other obligations	139,955	140,975
Other liabilities	8,269	6,884
Partners'/members' capital (deficit)	107,424	67,430
Total liabilities and partners'/members' capital (deficit)	255,648	215,289
Company's investments in unconsolidated joint ventures, net	63,799	32,015
Plaza VIII & IX Associates [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	8,182	8,335
Other assets	1,108	933
Total assets	9,290	9,268
Other liabilities	532	531
Partners'/members' capital (deficit)	8,758	8,737
Total liabilities and partners'/members' capital (deficit)	9,290	9,268
Company's investments in unconsolidated joint ventures, net	4,301	4,291
Harborside South Pier [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	58,492	59,733
Other assets	13,189	12,840
Total assets	71,681	72,573
Mortgages, loans payable and other obligations	70,411	70,690
Other liabilities	6,344	4,982
Partners'/members' capital (deficit)	(5,074)	(3,099)
Total liabilities and partners'/members' capital (deficit)	71,681	72,573
Company's investments in unconsolidated joint ventures, net	(1,331)	(343)
Red Bank Corporate Plaza [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	22,745	22,903
Other assets	3,108	2,909
Total assets	25,853	25,812
Mortgages, loans payable and other obligations	17,914	18,100
Other liabilities	138	117
Partners'/members' capital (deficit)	7,801	7,595
Total liabilities and partners'/members' capital (deficit)	25,853	25,812
Company's investments in unconsolidated joint ventures, net	3,787	3,676
Gramercy Agreement [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	39,025	39,276
Other assets	5,713	5,669
Total assets	44,738	44,945
Mortgages, loans payable and other obligations	50,978	50,978
Other liabilities	1,255	1,086
Partners'/members' capital (deficit)	(7,495)	(7,119)
Total liabilities and partners'/members' capital (deficit)	44,738	44,945
12 Vreeland [Member]
Schedule of Equity Method Investments [Line Items]
Rental property, net	14,144	13,122
Other assets	484	521
Total assets	14,628	13,643
Mortgages, loans payable and other obligations	652	1,207
Other liabilities		168
Partners'/members' capital (deficit)	13,976	12,268
Total liabilities and partners'/members' capital (deficit)	14,628	13,643
Company's investments in unconsolidated joint ventures, net	10,432	10,233
Boston-Downtown Crossing [Member]
Schedule of Equity Method Investments [Line Items]
Other assets	45,986	46,121
Total assets	45,986	46,121
Partners'/members' capital (deficit)	45,986	46,121
Total liabilities and partners'/members' capital (deficit)	45,986	46,121
Company's investments in unconsolidated joint ventures, net	13,049	13,005
Gale Jefferson [Member]
Schedule of Equity Method Investments [Line Items]
Other assets	2,987	2,927
Total assets	2,987	2,927
Partners'/members' capital (deficit)	2,987	2,927
Total liabilities and partners'/members' capital (deficit)	2,987	2,927
Company's investments in unconsolidated joint ventures, net	1,173	1,153
Stamford SM LLC [Member]
Schedule of Equity Method Investments [Line Items]
Other assets	40,485
Total assets	40,485
Partners'/members' capital (deficit)	40,485
Total liabilities and partners'/members' capital (deficit)	40,485
Company's investments in unconsolidated joint ventures, net	$ 32,388