Property Dispositions and Assets Held for Sale (Details) (USD $)	3 Months Ended	6 Months Ended		1 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2012 sqft	Jun. 30, 2011	May 31, 2011 Property at 28 West 44th Street sqft	Feb. 29, 2012 292 Madison Avenue	Jun. 30, 2012 292 Madison Avenue
Property Dispositions and Assets Held for Sale
Consideration for sale of property				$ 161,000,000	$ 85,000,000
Square footage of property		30,776,460		359,000
Gain on sale of property	46,085,000	6,627,000	46,085,000	46,100,000		6,600,000
Revenues
Rental revenue	3,194,000	516,000	8,735,000
Escalation and reimbursement revenues	219,000		873,000
Other income	56,000		60,000
Total revenues	3,469,000	516,000	9,668,000
Operating expense	498,000	(3,000)	1,645,000
Real estate taxes	188,000		1,034,000
Interest expense, net of interest income	1,101,000	597,000	2,604,000
Amortization of deferred financing costs	6,000		160,000
Depreciation and amortization			676,000
Total expenses	1,793,000	594,000	6,119,000
Net income (loss) from discontinued operations	$ 1,676,000	$ (78,000)	$ 3,549,000