Investment in Unconsolidated Joint Ventures (Details 2) (USD $)	3 Months Ended																																					1 Months Ended									3 Months Ended													3 Months Ended				3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014 Joint Venture	Dec. 31, 2013 Joint Venture	Mar. 31, 2014 Joint Venture 7 Renaissance		Dec. 31, 2013 Joint Venture 7 Renaissance	Mar. 31, 2014 Joint Venture 11 West 34th Street		Dec. 31, 2013 Joint Venture 11 West 34th Street	Mar. 31, 2014 Joint Venture 280 Park Avenue		Dec. 31, 2013 Joint Venture 280 Park Avenue	Mar. 31, 2014 Joint Venture 1745 Broadway		Dec. 31, 2013 Joint Venture 1745 Broadway	Mar. 31, 2014 Joint Venture 1 and 2 Jericho Plaza		Dec. 31, 2013 Joint Venture 1 and 2 Jericho Plaza	Mar. 31, 2014 Joint Venture 800 Third Avenue		Dec. 31, 2013 Joint Venture 800 Third Avenue	Mar. 31, 2014 Joint Venture 388 and 390 Greenwich Street		Dec. 31, 2013 Joint Venture 388 and 390 Greenwich Street		Mar. 31, 2014 Joint Venture 388 and 390 Greenwich Street Mortgage loan	Mar. 31, 2014 Joint Venture 388 and 390 Greenwich Street Mezzanine loans	Mar. 31, 2014 Joint Venture 315 West 36th Street		Dec. 31, 2013 Joint Venture 315 West 36th Street	Mar. 31, 2014 Joint Venture 717 Fifth Avenue Mortgage loan	Mar. 31, 2014 Joint Venture 717 Fifth Avenue Mezzanine loans	Mar. 31, 2014 Joint Venture 21 East 66th Street		Dec. 31, 2013 Joint Venture 21 East 66th Street	Feb. 28, 2014 Joint Venture 100 Park Avenue	Mar. 31, 2014 Joint Venture 100 Park Avenue		Dec. 31, 2013 Joint Venture 100 Park Avenue		Mar. 31, 2014 Joint Venture 21 West 34th Street		Dec. 31, 2013 Joint Venture 21 West 34th Street		Mar. 31, 2014 Joint Venture 1604-1610 Broadway		Dec. 31, 2013 Joint Venture 1604-1610 Broadway		Mar. 31, 2014 Joint Venture 747 Madison Avenue		Dec. 31, 2013 Joint Venture 747 Madison Avenue	Mar. 31, 2014 Joint Venture 180/182 Broadway		Dec. 31, 2013 Joint Venture 180/182 Broadway	Mar. 31, 2014 Joint Venture The Meadows		Dec. 31, 2013 Joint Venture The Meadows	Mar. 31, 2014 Joint Venture 3 Columbus Circle		Dec. 31, 2013 Joint Venture 3 Columbus Circle		Mar. 31, 2014 Joint Venture 1552 Broadway extension		Dec. 31, 2013 Joint Venture 1552 Broadway		Mar. 31, 2014 Joint Venture 1552 Broadway Mortgage loan	Mar. 31, 2014 Joint Venture 1552 Broadway Mezzanine loans	Mar. 31, 2014 Joint Venture Other loan payable		Dec. 31, 2013 Joint Venture Other loan payable	Mar. 31, 2014 Joint Venture 724 Fifth Avenue		Dec. 31, 2013 Joint Venture 724 Fifth Avenue		Mar. 31, 2014 Joint Venture 10 East 53rd Street		Dec. 31, 2013 Joint Venture 10 East 53rd Street	Mar. 31, 2014 Joint Venture 33 Beekman		Dec. 31, 2013 Joint Venture 33 Beekman		Mar. 31, 2014 Joint Venture 600 Lexington Avenue		Dec. 31, 2013 Joint Venture 600 Lexington Avenue	Mar. 31, 2014 Joint Venture 521 Fifth Avenue		Dec. 31, 2013 Joint Venture 521 Fifth Avenue	Mar. 31, 2014 Joint Venture West Coast office portfolio		Dec. 31, 2013 Joint Venture West Coast office portfolio		Mar. 31, 2014 Joint Venture Initial Maturity July 2022 717 Fifth Avenue		Dec. 31, 2013 Joint Venture Initial Maturity July 2022 717 Fifth Avenue		Mar. 31, 2014 Joint Venture Initial Maturity July 2024 717 Fifth Avenue		Dec. 31, 2013 Joint Venture Initial Maturity July 2024 717 Fifth Avenue		Apr. 30, 2014 Joint Venture Subsequent Event 724 Fifth Avenue Mortgage loan	Apr. 30, 2014 Joint Venture Subsequent Event 724 Fifth Avenue Mezzanine loans
First mortgage notes and other loan payable
Interest rate, fixed rate debt (as a percent)						10.00%	[1]		4.82%	[1]		6.57%	[1]		5.68%	[1]		5.65%	[1]		6.00%	[1]		3.20%	[1],[2]					3.16%	[1]				3.60%	[1]											0.00%	[1],[3]																																														4.45%	[1],[4]			9.00%	[1],[4]
Interest rate, floating rate debt (as a percent)																								1.31%	[1],[2]										2.87%	[1]			4.28%	[1],[5]											2.94%	[1]		2.91%	[1]		7.75%	[1]		2.34%	[1],[6]			4.07%	[1],[7]					1.06%	[1]		2.51%	[1],[8]			2.66%	[1]		2.91%	[1],[9]			2.24%	[1]		2.36%	[1]		0.00%	[1],[10]
Total fixed rate debt	$ 4,122,502,000		$ 4,130,629,000	$ 2,887,738,000	$ 3,223,895,000	$ 1,276,000		$ 1,276,000	$ 17,129,000		$ 17,205,000	$ 705,082,000		$ 706,886,000	$ 340,000,000		$ 340,000,000	$ 163,750,000		$ 163,750,000	$ 20,910,000		$ 20,910,000	$ 996,082,000	[2]	$ 996,082,000	[2]			$ 25,000,000		$ 25,000,000	$ 300,000,000	$ 290,000,000	$ 12,000,000		$ 12,000,000		$ 0	[5]	$ 209,786,000	[5]	$ 0	[11]	$ 100,000,000	[11]	$ 0	[3]	$ 27,000,000	[3]																																												$ 300,000,000	[4]	$ 300,000,000	[4]	$ 306,509,000	[4]	$ 304,000,000	[4]
Total floating rate debt	848,520,000		729,949,000	1,689,440,000	1,842,815,000																			142,297,000	[2]	142,297,000	[2]	72,000,000	70,300,000						1,940,000		1,959,000		360,000,000	[5]	0	[5]									33,125,000		33,125,000	89,778,000		89,893,000	67,350,000		67,350,000	237,189,000	[6]	239,233,000	[6]	169,283,000	[7]	158,690,000	[7]			30,000,000		30,000,000	119,765,000	[8]	120,000,000	[8]	125,000,000		125,000,000	24,057,000	[9]	18,362,000	[9]	119,656,000		120,616,000	170,000,000		170,000,000	0	[10]	526,290,000	[10]
Total mortgages and other loans payable	4,971,022,000		4,860,578,000	4,577,178,000	5,066,710,000																							576,000,000	562,400,000
Maximum amount of loan recourse to entity																													200,000,000.0																																																			75,000,000
Face amount of loan																																						360,000,000																																																																235,000,000	40,000,000
Term of refinanced mortgage																																						7 years
Gain (loss) on early extinguishment of debt	3,000	(18,513,000)																																				3,200,000
Incentive income																																															7,700,000
Possible increase in mortgage based on meeting certain performance hurdles																																																												40,000,000.0
Committed amount																																																																				150,000,000	41,500,000
Number of extension options (extensions)																																																																2
Period of extension option for mortgage secured by the portfolio																																																																1 year
Unfunded amount																																																																				$ 12,200,000	$ 10,000,000

[1] Effective weighted average interest rate for the three months ended March 31, 2014, taking into account interest rate hedges in effect during the period.

[2] These loans are comprised of a $576.0 million mortgage and a $562.4 million mezzanine loan, both of which are fixed rate loans, except for $72.0 million of the mortgage and $70.3 million of the mezzanine loan which are floating. Up to $200.0 million of the mezzanine loan, secured indirectly by these properties, is recourse to us. We believe it is unlikely that we will be required to perform under this guarantee.

[3] This loan was in default since November 2009 due to the non-payment of debt service. In January 2014, the joint venture relinquished its ground lease position to the lender. During the three months ended March 31, 2014, we also recognized $7.7 million of incentive income, which is included in other income on the consolidated statements of income.

[4] These loans are comprised of a $300.0 million fixed rate mortgage loan and $290.0 million mezzanine loan. The mezzanine loan is subject to accretion based on the difference between contractual interest rate and contractual pay rate.

[5] In February 2014, the joint venture replaced the previous fixed rate mortgage with a $360.0 million, seven-year floating rate, mortgage and realized a net loss on early extinguishment of $3.2 million.

[6] The joint venture has the ability to increase the mortgage by $40.0 million based on meeting certain performance hurdles. In connection with this obligation, we executed a master lease agreement and our joint venture partner executed a contribution agreement to reflect its pro rata obligation under the master lease. The lien on the mortgage and the master lease excludes the condominium interest owned by Y&R. See Note 5 of prior table.

[7] These loans are comprised of a $150.0 million mortgage loan and a $41.5 million mezzanine loan and are subject to two one-year extension options. As of March 31, 2014, $12.2 million of the mortgage loan and $10.0 million of the mezzanine loan remained unfunded.

[8] In April 2014, the joint venture refinanced the mortgage with a $235.0 million mortgage and a $40.0 million mezzanine loan. These new floating rate loans mature in April 2017.

[9] This loan has a committed amount of $75.0 million, which is recourse to us. Our partner has indemnified us for its pro rata share of the recourse guarantee. A portion of the guarantee terminates upon the joint venture reaching certain milestones. We believe it is unlikely that we will be required to perform under this guarantee.

[10] In March 2014, we sold our interest in the joint venture, inclusive of our share in the joint venture debt.

[11] In January 2014, we sold our interest in the joint venture, inclusive of our share of the joint venture debt.