Investments In Unconsolidated Joint Ventures (Summary Of The Results Of Financial Position) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Rental property, net	$ 148,073	$ 152,372
Other assets	72,723	75,992
Total assets	220,796	228,364
Mortgages, loans payable and other obligations	143,425	146,731
Other liabilities	6,804	7,305
Partners'/members' capital (deficit)	70,567	74,328
Total liabilities and partners'/members' capital (deficit)	220,796	228,364
Company's investment in unconsolidated joint ventures, net	32,673	34,220
Plaza VIII & IX Associates [Member]
Rental property, net	8,641	8,947
Other assets	1,253	906
Total assets	9,894	9,853
Other liabilities	529	529
Partners'/members' capital (deficit)	9,365	9,324
Total liabilities and partners'/members' capital (deficit)	9,894	9,853
Company's investment in unconsolidated joint ventures, net	4,605	4,584
Harborside South Pier [Member]
Rental property, net	62,179	64,964
Other assets	13,428	11,681
Total assets	75,607	76,645
Mortgages, loans payable and other obligations	71,639	72,168
Other liabilities	5,044	4,356
Partners'/members' capital (deficit)	(1,076)	121
Total liabilities and partners'/members' capital (deficit)	75,607	76,645
Company's investment in unconsolidated joint ventures, net	568	1,161
Red Bank Corporate Plaza [Member]
Rental property, net	23,214	23,594
Other assets	2,621	6,422
Total assets	25,835	30,016
Mortgages, loans payable and other obligations	18,520	20,424
Other liabilities	50	89
Partners'/members' capital (deficit)	7,265	9,503
Total liabilities and partners'/members' capital (deficit)	25,835	30,016
Company's investment in unconsolidated joint ventures, net	3,495	4,598
Gramercy Agreement [Member]
Rental property, net	39,732	40,786
Other assets	5,983	6,261
Total assets	45,715	47,047
Mortgages, loans payable and other obligations	50,978	50,978
Other liabilities	1,105	1,719
Partners'/members' capital (deficit)	(6,368)	(5,650)
Total liabilities and partners'/members' capital (deficit)	45,715	47,047
Princeton Forrestal Village [Member]
Other assets	196	1,435
Total assets	196	1,435
Other liabilities	76	612
Partners'/members' capital (deficit)	120	823
Total liabilities and partners'/members' capital (deficit)	196	1,435
Gale Kimball [Member]
Other assets	46	51
Total assets	46	51
Partners'/members' capital (deficit)	46	51
Total liabilities and partners'/members' capital (deficit)	46	51
12 Vreeland [Member]
Rental property, net	14,307	14,081
Other assets	497	734
Total assets	14,804	14,815
Mortgages, loans payable and other obligations	2,288	3,161
Partners'/members' capital (deficit)	12,516	11,654
Total liabilities and partners'/members' capital (deficit)	14,804	14,815
Company's investment in unconsolidated joint ventures, net	9,969	9,860
Boston-Downtown Crossing [Member]
Other assets	46,111	46,062
Total assets	46,111	46,062
Partners'/members' capital (deficit)	46,111	46,062
Total liabilities and partners'/members' capital (deficit)	46,111	46,062
Company's investment in unconsolidated joint ventures, net	12,998	13,022
Gale Jefferson [Member]
Other assets	2,588	2,440
Total assets	2,588	2,440
Partners'/members' capital (deficit)	2,588	2,440
Total liabilities and partners'/members' capital (deficit)	2,588	2,440
Company's investment in unconsolidated joint ventures, net	$ 1,038	$ 995