Property Acquisitions - Schedule of Fair Value of Equity Interest Immediately Before Acquisition Date (Details) - USD ($) $ in Thousands		1 Months Ended				12 Months Ended
	Nov. 30, 2015	Dec. 31, 2015	Aug. 31, 2015	Jul. 31, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2016	Mar. 31, 2016
Property Acquisitions
Operating Leases, Income Statement, Minimum Lease Revenue						$ 1,100,993	$ 1,323,767	$ 1,245,981
Depreciation and amortization						403,320	821,041	$ 560,887
183, 187 Broadway & 5-7 Dey Street
Property Acquisitions
Land			$ 20,266
Building and building leasehold			42,468
Contract purchase price			63,146
Net consideration funded by us at closing, excluding consideration financed by debt			0
Debt assumed			0
Equity and/or debt investment held			0
600 Lexington Avenue
Property Acquisitions
Land						81,670
Building and building leasehold						182,447
Contract purchase price	$ 284,000					$ 284,000
Net consideration funded by us at closing, excluding consideration financed by debt	(79,085)	$ (79,085)
Debt assumed	(112,795)	(112,795)
Fair value of retained equity interest	92,120
Equity and/or debt investment held	(54,575)	(54,575)
Other	2,533
Purchase price fair value adjustment	$ 40,078	$ 40,100
11 Madison Avenue
Property Acquisitions
Land			675,776
Building and building leasehold			1,553,602
Contract purchase price			2,428,359
Net consideration funded by us at closing, excluding consideration financed by debt			0
Debt assumed			0
Equity and/or debt investment held			0
110 Greene Street
Property Acquisitions
Land				$ 45,120
Building and building leasehold				215,470
Contract purchase price				255,000
Net consideration funded by us at closing, excluding consideration financed by debt				0
Debt assumed				0
Equity and/or debt investment held				0
1640 Flatbush Avenue
Property Acquisitions
Land										$ 6,226
Building and building leasehold										501
Contract purchase price										6,800
Net consideration funded by us at closing, excluding consideration financed by debt					$ 0
Debt assumed					0
Equity and/or debt investment held					$ 0
Upper East Side Residential, 11 Madison Avenue, 600 Lexington Ave, 187 Broadway and 5 & 7 Dey Street, 110 Greene Street and 1640 Flatbush Avenue
Property Acquisitions
Operating Leases, Income Statement, Minimum Lease Revenue							7,800
Depreciation and amortization							$ 18,500
As Previously Reported | 183, 187 Broadway & 5-7 Dey Street
Property Acquisitions
Land			22,100
Building and building leasehold			41,000
As Previously Reported | 11 Madison Avenue
Property Acquisitions
Land			849,900
Building and building leasehold			$ 1,600,000
As Previously Reported | 110 Greene Street
Property Acquisitions
Land				89,300
Building and building leasehold				$ 165,800
As Previously Reported | Upper East Side Residential
Property Acquisitions
Land									$ 17,500
Building and building leasehold									$ 32,500
As Previously Reported | 1640 Flatbush Avenue
Property Acquisitions
Land										6,100
Building and building leasehold										$ 700