Property Acquisitions (Details) - USD ($)			1 Months Ended										12 Months Ended
	Nov. 30, 2015	Apr. 30, 2014	Mar. 31, 2016	Dec. 31, 2015	Aug. 31, 2015	Jul. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Oct. 31, 2014	Sep. 30, 2014	Jul. 31, 2014	May 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Recognized Identifiable Assets Acquired and Liabilities Assumed
Issuance of aggregate liquidation preference of preferred units				$ 221,932,000									$ 221,932,000	$ 221,932,000
Impact to rental revenue for amortization of aggregate below-market leases													1,323,767,000	1,245,981,000	$ 1,121,066,000
Impact to depreciation expense													821,041,000	560,887,000	$ 371,610,000
Total fixed rate debt				5,816,010,000									3,518,127,000	5,816,010,000
600 Lexington Ave [Member] | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land				97,000,000										97,000,000
Building and building leasehold				180,200,000										$ 180,200,000
183 Broadway [Member]
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land			$ 5,799,000
Building and building leasehold			23,431,000
Above market lease value			0
Acquired in-place leases			773,000
Other assets, net of other liabilities			20,000
Assets acquired			30,023,000
Mark-to-market assumed debt			0
Below market lease value			(1,523,000)
Derivatives			0
Liabilities assumed			(1,523,000)
Purchase price			28,500,000
Net consideration funded by us at closing, excluding consideration financed by debt			28,500,000
Equity and/or debt investment held			0
Debt assumed			0
Impact to rental revenue for amortization of aggregate below-market leases													200,000
Impact to depreciation expense													2,100,000
183 Broadway [Member] | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land			26,600,000
Building and building leasehold			$ 0
600 Lexington Avenue
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land													81,670,000
Building and building leasehold													182,447,000
Above market lease value													3,320,000
Acquired in-place leases													22,449,000
Other assets, net of other liabilities													0
Assets acquired													289,886,000
Mark-to-market assumed debt													(55,000)
Below market lease value													(5,831,000)
Derivatives													0
Liabilities assumed													(5,886,000)
Purchase price	$ 284,000,000												$ 284,000,000
Net consideration funded by us at closing, excluding consideration financed by debt	79,085,000			79,085,000
Equity and/or debt investment held	54,575,000			54,575,000
Debt assumed	112,795,000			112,795,000
Ownership interest in consolidated joint venture (as a percent)													45.00%
Value of interest													$ 277,300,000
Purchase price fair value adjustment	$ 40,078,000			$ 40,100,000
183, 187 Broadway & 5-7 Dey Street
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land					$ 20,266,000
Building and building leasehold					42,468,000
Above market lease value					17,000
Acquired in-place leases					3,621,000
Other assets, net of other liabilities					0
Assets acquired					66,372,000
Mark-to-market assumed debt					0
Below market lease value					(3,226,000)
Derivatives					0
Liabilities assumed					(3,226,000)
Purchase price					63,146,000
Net consideration funded by us at closing, excluding consideration financed by debt					0
Equity and/or debt investment held					0
Debt assumed					0
183, 187 Broadway & 5-7 Dey Street | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land					22,100,000
Building and building leasehold					41,000,000
183, 187 Broadway & 5-7 Dey Street | Series R Preferred Units
Recognized Identifiable Assets Acquired and Liabilities Assumed
Issuance of aggregate liquidation preference of preferred units													10,000,000
183, 187 Broadway & 5-7 Dey Street | Series S Preferred Units
Recognized Identifiable Assets Acquired and Liabilities Assumed
Issuance of aggregate liquidation preference of preferred units													26,900,000
11 Madison Avenue
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land					675,776,000
Building and building leasehold					1,553,602,000
Above market lease value					19,764,000
Acquired in-place leases					366,949,000
Other assets, net of other liabilities					0
Assets acquired					2,616,091,000
Mark-to-market assumed debt					0
Below market lease value					(187,732,000)
Derivatives					0
Liabilities assumed					(187,732,000)
Purchase price					2,428,359,000
Net consideration funded by us at closing, excluding consideration financed by debt					0
Equity and/or debt investment held					0
Debt assumed					0
11 Madison Avenue | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land					849,900,000
Building and building leasehold					$ 1,600,000,000
110 Greene Street
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land						$ 45,120,000
Building and building leasehold						215,470,000
Above market lease value						0
Acquired in-place leases						8,967,000
Other assets, net of other liabilities						0
Assets acquired						269,557,000
Mark-to-market assumed debt						0
Below market lease value						(14,557,000)
Derivatives						0
Liabilities assumed						(14,557,000)
Purchase price						255,000,000
Net consideration funded by us at closing, excluding consideration financed by debt						0
Equity and/or debt investment held						0
Debt assumed						$ 0
Ownership interest in consolidated joint venture (as a percent)						90.00%
110 Greene Street | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land						$ 89,300,000
Building and building leasehold						165,800,000
110 Greene Street | Series P Preferred Units
Recognized Identifiable Assets Acquired and Liabilities Assumed
Issuance of aggregate liquidation preference of preferred units						5,000,000
110 Greene Street | Series Q Preferred Units
Recognized Identifiable Assets Acquired and Liabilities Assumed
Issuance of aggregate liquidation preference of preferred units						$ 6,700,000
Upper East Side Residential
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land							$ 48,152,000
Building and building leasehold							0
Above market lease value							0
Acquired in-place leases							1,922,000
Other assets, net of other liabilities							0
Assets acquired							50,074,000
Mark-to-market assumed debt							0
Below market lease value							0
Derivatives							0
Liabilities assumed							0
Purchase price							50,074,000
Net consideration funded by us at closing, excluding consideration financed by debt							0
Equity and/or debt investment held							0
Debt assumed							$ 0
Ownership interest in consolidated joint venture (as a percent)							95.10%
Upper East Side Residential | Series N Preferred Units
Recognized Identifiable Assets Acquired and Liabilities Assumed
Issuance of aggregate liquidation preference of preferred units							$ 13,800,000
1640 Flatbush Avenue
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land								$ 6,226,000
Building and building leasehold								501,000
Above market lease value								0
Acquired in-place leases								146,000
Other assets, net of other liabilities								0
Assets acquired								6,873,000
Mark-to-market assumed debt								0
Below market lease value								(73,000)
Derivatives								0
Liabilities assumed								(73,000)
Purchase price								6,800,000
Net consideration funded by us at closing, excluding consideration financed by debt								0
Equity and/or debt investment held								0
Debt assumed								0
1640 Flatbush Avenue | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land								6,100,000
Building and building leasehold								$ 700,000
102 Greene Street
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land									$ 8,215,000
Building and building leasehold									26,717,000
Above market lease value									0
Acquired in-place leases									1,015,000
Other assets, net of other liabilities									3,000
Assets acquired									35,950,000
Mark-to-market assumed debt									0
Below market lease value									(3,701,000)
Derivatives									0
Liabilities assumed									(3,701,000)
Purchase price									32,249,000
Net consideration funded by us at closing, excluding consideration financed by debt									32,249,000
Equity and/or debt investment held									0
Debt assumed									0
102 Greene Street | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land									11,300,000
Building and building leasehold									21,000,000
635 Madison Avenue
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land										$ 205,632,000
Building and building leasehold										15,805,000
Above market lease value										0
Acquired in-place leases										17,345,000
Other assets, net of other liabilities										0
Assets acquired										238,782,000
Mark-to-market assumed debt										0
Below market lease value										(85,036,000)
Derivatives										0
Liabilities assumed										(85,036,000)
Purchase price										153,746,000
Net consideration funded by us at closing, excluding consideration financed by debt										153,746,000
Equity and/or debt investment held										0
Debt assumed										0
635 Madison Avenue | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land										$ 153,700,000
719 Seventh Avenue
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land											$ 41,850,000
Building and building leasehold											0
Above market lease value											0
Acquired in-place leases											0
Other assets, net of other liabilities											0
Assets acquired											41,850,000
Mark-to-market assumed debt											0
Below market lease value											0
Derivatives											0
Liabilities assumed											0
Purchase price											41,850,000
Net consideration funded by us at closing, excluding consideration financed by debt											41,850,000
Equity and/or debt investment held											0
Debt assumed											$ 0
Ownership interest in consolidated joint venture (as a percent)											75.00%
719 Seventh Avenue | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land											$ 14,400,000
Building and building leasehold											26,700,000
719 Seventh Avenue | Series L Preferred Units
Recognized Identifiable Assets Acquired and Liabilities Assumed
Issuance of aggregate liquidation preference of preferred units											14,100,000
719 Seventh Avenue | Series K Preferred Units
Recognized Identifiable Assets Acquired and Liabilities Assumed
Issuance of aggregate liquidation preference of preferred units											9,500,000
115 Spring Street
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land											11,078,000
Building and building leasehold											44,799,000
Above market lease value											0
Acquired in-place leases											2,037,000
Other assets, net of other liabilities											0
Assets acquired											57,914,000
Mark-to-market assumed debt											0
Below market lease value											(4,789,000)
Derivatives											0
Liabilities assumed											(4,789,000)
Purchase price											53,125,000
Net consideration funded by us at closing, excluding consideration financed by debt											53,125,000
Equity and/or debt investment held											0
Debt assumed											0
115 Spring Street | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land											15,900,000
Building and building leasehold											$ 37,200,000
388-390 Greenwich Street
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land												$ 516,292,000
Building and building leasehold												964,434,000
Above market lease value												0
Acquired in-place leases												302,430,000
Other assets, net of other liabilities												6,495,000
Assets acquired												1,789,651,000
Mark-to-market assumed debt												0
Below market lease value												(186,782,000)
Derivatives												(18,001,000)
Liabilities assumed												(204,783,000)
Purchase price		$ 1,585,000,000										1,584,868,000
Net consideration funded by us at closing, excluding consideration financed by debt		208,614,000										208,614,000
Equity and/or debt investment held		(148,025,000)										148,025,000
Debt assumed		1,162,379,000										1,162,379,000
Value of interest												1,585,000,000
Purchase price fair value adjustment		$ 71,446,000										$ 71,400,000
Economic interest (as a percent)												49.65%
Face amount of loan												$ 1,450,000,000
Notional value												504,000,000
Total fixed rate debt									$ 500,000,000
388-390 Greenwich Street | As Previously Reported
Recognized Identifiable Assets Acquired and Liabilities Assumed
Land												558,700,000
Building and building leasehold												$ 1,000,000,000
102 Greene Street, 635 Madison Avenue, 719 Seventh Avenue, 115 Spring Street, and 388-390 Greenwich Street
Recognized Identifiable Assets Acquired and Liabilities Assumed
Impact to rental revenue for amortization of aggregate below-market leases													7,600,000
Impact to depreciation expense													$ 10,300,000