Commitments and Contingencies (Details 2) (USD $)			1 Months Ended			12 Months Ended	1 Months Ended		12 Months Ended				1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Oct. 31, 2009 420 Lexington Avenue	Jun. 30, 2009 420 Lexington Avenue	Mar. 31, 1998 420 Lexington Avenue	Dec. 31, 2011 420 Lexington Avenue	Jul. 31, 2016 711 Third Avenue	Jul. 31, 2011 711 Third Avenue	Dec. 31, 2011 711 Third Avenue	Dec. 31, 2011 461 Fifth Avenue y option	Dec. 31, 2011 625 Madison Avenue y option	Dec. 31, 2011 1185 Avenue of the Americas. y	Apr. 30, 1988 673 First Avenue y	Dec. 31, 2011 673 First Avenue y	Dec. 31, 2010 673 First Avenue
Commitments and Contingencies
Required annual ground lease payments					$ 6,000,000	$ 10,900,000	$ 5,500,000		$ 5,250,000	$ 2,100,000	$ 4,600,000	$ 6,900,000
Required sub-leasehold position payments					1,100,000
Operating sub-leasehold position acquired			7,600,000	7,700,000
Required annual ground lease payments, prior to reset								1,550,000
Percentage of fee not owned by the entity									50.00%
Number of renewal options available										2	2
Term of first renewal option (in years)										21	23	23	26
Term of second renewal option (in years)										21	23
Term of third renewal option (in years)										15
Land as percentage of fair market value of the property													70.00%
Initial lease term (in years)													49
Lease year lessor is entitled to additional rent														11
Second lease year lessor is entitled to additional rent														25
Capital lease, cost basis	12,208,000	12,208,000												12,200,000
Cumulative amortization														$ 6,000,000	$ 5,800,000