Property Dispositions and Assets Held for Sale (Details) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Feb. 29, 2012 292 Madison Avenue	Feb. 28, 2013 44th West 55th Street
Property Dispositions and Assets Held for Sale
Consideration for sale of property			$ 85,000,000	$ 6,300,000
Gain on sale of property	1,113,000	6,627,000	6,600,000	1,100,000
Revenues
Rental revenue	(10,000)	568,000
Escalation and reimbursement revenues		7,000
Total revenues	(10,000)	575,000
Rental revenue	(10,000)	568,000
Operating expense	5,000	11,000
Real estate taxes	10,000	18,000
Interest expense, net of interest income		598,000
Transaction related costs		95,000
Depreciation and amortization	7,000	14,000
Total expenses	22,000	736,000
Net loss from discontinued operations	(32,000)	(161,000)
Total expenses	$ 22,000	$ 736,000