Investment in Unconsolidated Joint Ventures (Details 2) (USD $)	3 Months Ended		6 Months Ended			6 Months Ended																																6 Months Ended				1 Months Ended									6 Months Ended										6 Months Ended				6 Months Ended														6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 388 and 390 Greenwich Street		Dec. 31, 2013 388 and 390 Greenwich Street		Jun. 30, 2014 Joint Venture	Dec. 31, 2013 Joint Venture	Jun. 30, 2014 Joint Venture 7 Renaissance		Dec. 31, 2013 Joint Venture 7 Renaissance	Jun. 30, 2014 Joint Venture 11 West 34th Street		Dec. 31, 2013 Joint Venture 11 West 34th Street	Jun. 30, 2014 Joint Venture 280 Park Avenue		Dec. 31, 2013 Joint Venture 280 Park Avenue	Jun. 30, 2014 Joint Venture 1745 Broadway		Dec. 31, 2013 Joint Venture 1745 Broadway	Jun. 30, 2014 Joint Venture 1 and 2 Jericho Plaza		Dec. 31, 2013 Joint Venture 1 and 2 Jericho Plaza	Jun. 30, 2014 Joint Venture 800 Third Avenue		Dec. 31, 2013 Joint Venture 800 Third Avenue	Jun. 30, 2014 Joint Venture 315 West 36th Street		Dec. 31, 2013 Joint Venture 315 West 36th Street	Jun. 30, 2014 Joint Venture 717 Fifth Avenue Mortgage loan	Jun. 30, 2014 Joint Venture 717 Fifth Avenue Mezzanine loans	Jun. 30, 2014 Joint Venture 21 East 66th Street		Dec. 31, 2013 Joint Venture 21 East 66th Street	Jun. 30, 2014 Joint Venture 388 and 390 Greenwich Street		Dec. 31, 2013 Joint Venture 388 and 390 Greenwich Street		Feb. 28, 2014 Joint Venture 100 Park Avenue	Jun. 30, 2014 Joint Venture 100 Park Avenue		Dec. 31, 2013 Joint Venture 100 Park Avenue		Jun. 30, 2014 Joint Venture 21 West 34th Street		Dec. 31, 2013 Joint Venture 21 West 34th Street		Jun. 30, 2014 Joint Venture 1604-1610 Broadway		Dec. 31, 2013 Joint Venture 1604-1610 Broadway		Jun. 30, 2014 Joint Venture 180/182 Broadway		Dec. 31, 2013 Joint Venture 180/182 Broadway	Jun. 30, 2014 Joint Venture The Meadows		Dec. 31, 2013 Joint Venture The Meadows	Jun. 30, 2014 Joint Venture 3 Columbus Circle		Dec. 31, 2013 Joint Venture 3 Columbus Circle		Jun. 30, 2014 Joint Venture 1552 Broadway extension		Dec. 31, 2013 Joint Venture 1552 Broadway		Jun. 30, 2014 Joint Venture 1552 Broadway Mortgage loan	Jun. 30, 2014 Joint Venture 1552 Broadway Mezzanine loans	Jun. 30, 2014 Joint Venture Other loan payable		Dec. 31, 2013 Joint Venture Other loan payable	Jun. 30, 2014 Joint Venture 724 Fifth Avenue		Dec. 31, 2013 Joint Venture 724 Fifth Avenue		Apr. 30, 2014 Joint Venture 724 Fifth Avenue Mortgage loan	Jun. 30, 2014 Joint Venture 724 Fifth Avenue Mezzanine loans	Apr. 30, 2014 Joint Venture 724 Fifth Avenue Mezzanine loans	Jun. 30, 2014 Joint Venture 747 Madison Avenue		Dec. 31, 2013 Joint Venture 747 Madison Avenue	Jun. 30, 2014 Joint Venture 10 East 53rd Street		Dec. 31, 2013 Joint Venture 10 East 53rd Street	Jun. 30, 2014 Joint Venture 33 Beekman		Dec. 31, 2013 Joint Venture 33 Beekman		Jun. 30, 2014 Joint Venture 600 Lexington Avenue		Dec. 31, 2013 Joint Venture 600 Lexington Avenue	Jun. 30, 2014 Joint Venture 521 Fifth Avenue		Dec. 31, 2013 Joint Venture 521 Fifth Avenue	Jun. 30, 2014 Joint Venture West Coast office portfolio		Dec. 31, 2013 Joint Venture West Coast office portfolio		Jun. 30, 2014 Joint Venture Initial Maturity July 2022 717 Fifth Avenue		Dec. 31, 2013 Joint Venture Initial Maturity July 2022 717 Fifth Avenue		Jun. 30, 2014 Joint Venture Initial Maturity July 2024 717 Fifth Avenue		Dec. 31, 2013 Joint Venture Initial Maturity July 2024 717 Fifth Avenue
Mortgages and Other Loans Payable
Interest rate, fixed rate debt (as a percent)						3.80%	[1],[2]					10.00%	[1]		4.82%	[1]		6.57%	[1]		5.68%	[1]		5.65%	[1]		6.00%	[1]		3.16%	[1]				3.60%	[1]		0.00%	[1],[3]				0.00%				0.00%				0.00%	[1],[4]																																																	4.45%	[1],[5]			9.00%	[1],[5]
Total fixed rate debt	$ 4,622,075,000		$ 4,622,075,000		$ 4,130,629,000	$ 504,000,000	[2]	$ 0	[2]	$ 1,892,771,000	$ 3,223,895,000	$ 1,461,000		$ 1,276,000	$ 17,056,000		$ 17,205,000	$ 703,520,000		$ 706,886,000	$ 340,000,000		$ 340,000,000	$ 163,750,000		$ 163,750,000	$ 20,910,000		$ 20,910,000	$ 25,000,000		$ 25,000,000			$ 12,000,000		$ 12,000,000	$ 0	[3]	$ 996,082,000	[3]		$ 0	[6]	$ 209,786,000	[6]	$ 0	[7]	$ 100,000,000	[7]	$ 0	[4]	$ 27,000,000	[4]																																															$ 300,000,000	[5]	$ 300,000,000	[5]	$ 309,074,000	[5]	$ 304,000,000	[5]
Interest rate, floating rate debt (as a percent)						1.91%	[1],[2]																												2.88%	[1]		0.00%	[1],[3]				1.91%	[1],[6]											2.91%	[1]		7.75%	[1]		2.33%	[1],[8]			4.16%	[1],[9]					1.06%	[1]		2.58%	[1],[10]						0.00%	[1]		2.66%	[1]		2.91%	[1],[11]			2.23%	[1]		2.36%	[1]		0.00%	[1],[12]
Total floating rate debt	1,508,351,000		1,508,351,000		729,949,000	946,000,000	[2]	0	[2]	1,682,685,000	1,842,815,000																								1,921,000		1,959,000	0	[3]	142,297,000	[3]		360,000,000	[6]	0	[6]									89,551,000		89,893,000	67,350,000		67,350,000	235,129,000	[8]	239,233,000	[8]	175,904,000	[9]	158,690,000	[9]			30,000,000		30,000,000	275,000,000	[10]	120,000,000	[10]				0		33,125,000	125,000,000		125,000,000	34,141,000	[11]	18,362,000	[11]	118,689,000		120,616,000	170,000,000		170,000,000	0	[12]	526,290,000	[12]
Mortgages and other loans payable	6,130,426,000		6,130,426,000		4,860,578,000					3,575,456,000	5,066,710,000
Maximum amount of loan recourse to entity																																																																																							75,000,000
Face amount of loan						1,500,000,000																																				360,000,000																																				235,000,000		40,000,000
Term of refinanced mortgage						7 years																																				7 years
Loss on early extinguishment of debt	1,028,000	10,000	1,025,000	18,523,000																																		2,400,000				3,200,000																																					1,200,000
Incentive income																																																			7,700,000
Possible increase in mortgage based on meeting certain performance hurdles																																																													40,000,000.0
Committed amount																																	300,000,000	290,000,000																																			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																																																																					$ 8,400,000	$ 7,200,000

[1] Effective weighted average interest rate for the three months ended June 30, 2014, taking into account interest rate hedges in effect during the period.

[2] Simultaneous with the acquisition of our joint venture partner interest, we refinanced the $1.1 billion floating rate mortgage with a $1.5 billion seven-year floating rate mortgage, and have consolidated the property.

[3] In May 2014, we acquired the interest of our joint venture thereby consolidating the entity. Simultaneous with the acquisition, we refinanced the mortgage and realized a net loss on early extinguishment of debt of $2.4 million.

[4] 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 six months ended June 30, 2014, we also recognized $7.7 million of incentive income, which is included in other income on the consolidated statements of income.

[5] 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.

[6] 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.

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

[8] 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 3 of prior table.

[9] 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 June 30, 2014, $8.4 million of the mortgage loan and $7.2 million of the mezzanine loan remained unfunded.

[10] In April 2014, the joint venture refinanced the previous mortgage with a $235.0 million mortgage and a $40.0 million mezzanine loan and realized a net loss on early extinguishment of debt of $1.2 million. These new floating rate loans mature in April 2017.

[11] 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.

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