Property Dispositions (Details) (USD $)	3 Months Ended								12 Months Ended			1 Months Ended
	Dec. 31, 2013 sqft	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 sqft	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2013 300 Main Street	Aug. 30, 2013 333 West 34th Street	Feb. 28, 2013 44th West 55th Street	Feb. 29, 2012 292 Madison Avenue	May 31, 2011 Property at 28 West 44th Street sqft
Property Dispositions and Assets Held for Sale
Consideration for sale of property												$ 13,500,000	$ 220,300,000	$ 6,300,000	$ 85,000,000	$ 161,000,000
Asset impairment charges												2,200,000
Gain on sale of property	0	13,787,000	0	1,113,000	0	0	0	6,627,000	14,900,000	6,627,000	46,085,000		13,800,000	1,100,000	6,600,000	46,100,000
Employee compensation award													3,000,000		1,500,000
Area of property (sqft)	28,549,979								28,549,979							359,000
Revenues
Rental revenue									10,656,000	18,651,000	27,093,000
Escalation and reimbursement revenues									1,292,000	2,263,000	2,924,000
Other income									8,000	8,190,000	121,000
Total revenues									11,956,000	29,104,000	30,138,000
Operating expenses									3,643,000	6,646,000	7,424,000
Real estate taxes									765,000	1,224,000	2,334,000
Interest expense, net of interest income									461,000	2,082,000	4,922,000
Depreciable real estate reserves									2,150,000	0	0
Transaction related costs									0	160,000	1,000
Depreciation and amortization									3,212,000	6,373,000	6,715,000
Amortization of deferred financing costs									0	0	182,000
Total expenses									10,231,000	16,485,000	21,578,000
Net income from discontinued operations	$ 0	$ 1,406,000	$ (678,000)	$ 997,000	$ 9,737,000	$ 951,000	$ 899,000	$ 1,032,000	$ 1,725,000	$ 12,619,000	$ 8,560,000