Investment in Unconsolidated Joint Ventures (Details 2) (USD $)																																																													1 Months Ended					1 Months Ended	12 Months Ended				12 Months Ended				1 Months Ended																									1 Months Ended																				1 Months Ended	12 Months Ended		12 Months Ended			1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 33 Beekman	Dec. 31, 2013 16 Court Street		Dec. 31, 2012 16 Court Street		Dec. 31, 2013 Joint venture	Dec. 31, 2012 Joint venture	Dec. 31, 2013 Joint venture 100 Park Avenue		Dec. 31, 2012 Joint venture 100 Park Avenue	Dec. 31, 2013 Joint venture 7 Renaissance		Dec. 31, 2012 Joint venture 7 Renaissance	Dec. 31, 2013 Joint venture 11 West 34th Street		Dec. 31, 2012 Joint venture 11 West 34th Street	Dec. 31, 2013 Joint venture 280 Park Avenue		Dec. 31, 2012 Joint venture 280 Park Avenue	Dec. 31, 2013 Joint venture 21 West 34th Street		Dec. 31, 2012 Joint venture 21 West 34th Street	Dec. 31, 2013 Joint venture 1745 Broadway		Dec. 31, 2012 Joint venture 1745 Broadway	Dec. 31, 2013 Joint venture 1 and 2 Jericho Plaza		Dec. 31, 2012 Joint venture 1 and 2 Jericho Plaza	Dec. 31, 2013 Joint venture 800 Third Avenue		Dec. 31, 2012 Joint venture 800 Third Avenue	Dec. 31, 2013 Joint venture 388 and 390 Greenwich Street		Dec. 31, 2012 Joint venture 388 and 390 Greenwich Street		Dec. 31, 2013 Joint venture 388 and 390 Greenwich Street Mortgage loan	Dec. 31, 2013 Joint venture 388 and 390 Greenwich Street Mezzanine loans	Dec. 31, 2013 Joint venture 315 West 36th Street		Dec. 31, 2012 Joint venture 315 West 36th Street	Jun. 30, 2013 Joint venture 717 Fifth Avenue Mortgage loan	Sep. 30, 2012 Joint venture 717 Fifth Avenue Mortgage loan	Sep. 30, 2012 Joint venture 717 Fifth Avenue Mezzanine loans	Dec. 31, 2013 Joint venture 21 East 66th Street		Dec. 31, 2012 Joint venture 21 East 66th Street		Dec. 31, 2013 Joint venture 1604-1610 Broadway		Dec. 31, 2012 Joint venture 1604-1610 Broadway		Dec. 31, 2013 Joint venture West Coast office portfolio		Dec. 31, 2012 Joint venture West Coast office portfolio		Dec. 31, 2013 Joint venture 747 Madison Avenue		Dec. 31, 2012 Joint venture 747 Madison Avenue	Nov. 30, 2013 Joint venture 180/182 Broadway	Dec. 31, 2013 Joint venture 180/182 Broadway		Dec. 31, 2012 Joint venture 180/182 Broadway		Aug. 31, 2012 Joint venture The Meadows	Dec. 31, 2012 Joint venture The Meadows		Dec. 31, 2013 Joint venture The Meadows		Dec. 31, 2013 Joint venture 3 Columbus Circle		Dec. 31, 2012 Joint venture 3 Columbus Circle		Apr. 30, 2013 Joint venture 1552 Broadway extenstion_option	Dec. 31, 2013 Joint venture 1552 Broadway		Dec. 31, 2012 Joint venture 1552 Broadway		Dec. 31, 2013 Joint venture 1552 Broadway Mortgage loan	Apr. 30, 2013 Joint venture 1552 Broadway Mortgage loan	Dec. 31, 2013 Joint venture 1552 Broadway Mezzanine loans	Apr. 30, 2013 Joint venture 1552 Broadway Mezzanine loans	Dec. 31, 2013 Joint venture Other loan payable		Dec. 31, 2012 Joint venture Other loan payable	Dec. 31, 2013 Joint venture 724 Fifth Avenue		Dec. 31, 2012 Joint venture 724 Fifth Avenue	Dec. 31, 2013 Joint venture 10 East 53rd Street		Dec. 31, 2012 Joint venture 10 East 53rd Street	Dec. 31, 2013 Joint venture 33 Beekman		Dec. 31, 2012 Joint venture 33 Beekman		Dec. 31, 2013 Joint venture 600 Lexington Avenue		Dec. 31, 2012 Joint venture 600 Lexington Avenue	Nov. 30, 2012 Joint venture 521 Fifth Avenue	Dec. 31, 2013 Joint venture 521 Fifth Avenue		Dec. 31, 2012 Joint venture 521 Fifth Avenue	Dec. 31, 2013 Joint venture 27-29 West 34th Street		Dec. 31, 2012 Joint venture 27-29 West 34th Street		Dec. 31, 2013 Joint venture 16 Court Street		Dec. 31, 2012 Joint venture 16 Court Street		Dec. 31, 2013 Initial Maturity July 2022 Joint venture 717 Fifth Avenue		Dec. 31, 2012 Initial Maturity July 2022 Joint venture 717 Fifth Avenue		Dec. 31, 2013 Initial Maturity July 2024 Joint venture 717 Fifth Avenue		Dec. 31, 2012 Initial Maturity July 2024 Joint venture 717 Fifth Avenue		Sep. 30, 2012 West Coast office portfolio	Dec. 31, 2013 West Coast office portfolio property	Aug. 31, 2012 West Coast office portfolio	Dec. 31, 2013 West Coast office portfolio Joint venture Mezzanine loans	Dec. 31, 2013 West Coast office portfolio Joint venture Mortgage Loan	Dec. 31, 2013 3 Columbus Circle	Sep. 30, 2012 LIBOR 717 Fifth Avenue Mortgage loan	Dec. 31, 2013 LIBOR 16 Court Street
First mortgage notes and other loan payable
Interest rate, fixed rate debt (as a percent)										6.64%	[1]		10.00%	[1]		4.82%	[1]		6.57%	[1]		5.76%	[1]		5.68%	[1]		5.65%	[1]		6.00%	[1]		3.20%	[1],[2]					3.16%	[1]					4.10%	[1],[3]			5.66%	[1],[4]																																																													4.45%	[1],[5]			9.00%	[1],[5]
Interest rate, floating rate debt (as a percent)				3.22%	[1],[6]																													1.34%	[1],[2]											2.88%	[1]							3.93%	[1],[7]			2.97%	[1]			2.94%	[1],[8]						7.75%	[1],[9]	2.38%	[1],[10]				3.48%	[1],[11]							1.09%	[1]		2.54%	[1]		2.69%	[1]		2.94%	[1],[12]			2.28%	[1]			2.39%	[1]
Total fixed rate debt	$ 4,130,629,000	$ 3,457,769,000						$ 3,223,895,000	$ 3,219,885,000	$ 209,786,000		$ 212,287,000	$ 1,276,000		$ 856,000	$ 17,205,000		$ 17,491,000	$ 706,886,000		$ 710,000,000	$ 100,000,000		$ 100,000,000	$ 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	[3]	$ 12,000,000	[3]	$ 27,000,000	[4]	$ 27,000,000	[4]																																																											$ 300,000,000	[5]	$ 300,000,000	[5]	$ 304,000,000	[5]	$ 294,509,000	[5]
Total floating rate debt	729,949,000	1,157,695,000		79,243,000	[6]	0	[6]	1,842,815,000	2,138,163,000																									142,297,000	[2]	142,297,000	[2]	72,000,000	70,300,000							1,959,000		2,033,000						526,290,000	[7]	745,025,000	[7]	33,125,000		33,125,000		89,893,000	[8]	71,524,000	[8]		57,000,000	[9]	67,350,000	[9]	239,233,000	[10]	247,253,000	[10]		158,690,000	[11]	113,869,000	[11]					30,000,000		30,000,000	120,000,000		120,000,000	125,000,000		125,000,000	18,362,000	[12]	18,362,000	[12]	120,616,000		124,384,000		170,000,000		170,000,000	0	[13]	53,375,000	[13]	0	[14]	84,916,000	[14]
Total mortgages and other loans payable	4,860,578,000	4,615,464,000						5,066,710,000	5,358,048,000																													576,000,000	562,400,000
Maximum amount of loan recourse to entity			75,000,000					218,400,000																															200,000,000.0
Face amount of loan																																											245,000,000.0																																																																													68,000,000.0		26,700,000	20,500,000
Interest rate added to base rate (as a percent)																																																																																																																														2.75%	3.50%
Number of properties sold (properties)																																																																																																																									3
Repayments of loan																																																																																																																									194,500,000		20,500,000	194,500,000
Committed amount								60,000,000																																																						90,000,000				60,000,000			67,400,000						200,000,000.0						170,000,000.0		30,000,000.0
Period of extension option for mortgage secured by the portfolio																																																													1 year														1 year																																													1 year
Term of refinanced mortgage																																																																		3 years									3 years																									7 years																				2 years
Proceeds from sale of equity method investments																																																																			10,800,000																																																						224,300,000
Possible increase in mortgage based on meeting certain performance hurdles																																																																							40,000,000
Undrawn amount																																																																			3,000,000
Committed additional capital contribution funded																																																																																																																													260,000,000
Amount outstanding																																																																											119,600,000
Number of extension options (extension options)																																																																											2
Unfunded amount																																																																																$ 37,600,000		$ 3,700,000

[1] Effective weighted average interest rate for the year ended December 31, 2013, 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] In April 2013, the loan was refinanced at par and its maturity was extended to April 2023.

[4] This loan went into default in November 2009 due to the non-payment of debt service.

[5] In June 2012, the joint venture replaced the $245.0 million floating rate mortgage loan, which bore interest at 275 basis points over LIBOR and was due to mature in September 2012, with a $300.0 million fixed rate mortgage loan and $290.0 million mezzanine loan which is subject to accretion based on the difference between contractual interest rate and contractual pay rate.

[6] In April 2013, we acquired interests from our joint venture partner, CIF, and have consolidated the entity due to our controlling interest. In December 2013, we repaid $5.0 million of the principal balance and modified and extended the terms of the existing mortgage. The modified mortgage bears interest based on one-month LIBOR plus 350 basis points with a floor of 50 basis points.

[7] As a result of the sale of three of its properties, the joint venture paid down $194.5 million of its mortgage and $20.5 million of its mezzanine loan.

[8] This loan has a committed amount of $90.0 million. In November 2013, this loan was extended by one-year, subject to principal amortization through the maturity date

[9] As a result of the refinancing and restructuring in August 2012, we replaced the previous mortgage with a $60.0 million, three-year mortgage, of which $3.0 million was unfunded as of December 31, 2012, and recognized additional income of $10.8 million due to the repayment of the previous mortgage at a discount. In December 2013, the joint venture upsized the original mortgage with a maximum amount of $60.0 million to $67.4 million. All other terms of the loan remained the same.

[10] This loan has a committed amount of $260.0 million. 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 7 of prior table.

[11] In April 2013, we refinanced the previous $119.6 million mortgage with a $200.0 million three-year loan construction financing facility comprised of a $170.0 million mortgage loan and a $30.0 million mezzanine loan. The facility has two one-year extension options. As of December 31, 2013, $37.6 million of the mortgage loan and $3.7 million of the mezzanine loan remained unfunded.

[12] 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.

[13] In May 2013, this loan was refinanced and its maturity was extended to May 2018. In December 2013, we sold our interest in the joint venture, inclusive of our share in the joint venture debt.

[14] In April 2013, we acquired interests from our joint venture partner, CIF, and have consolidated the entity due to our controlling interest.