Schedule III - Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Real Estate And Accumulated Depreciation [Line Items]
Encumbrances				$ 3,599,800
Initial cost to company, Land				2,065,206
Initial cost to company, Building and Improvements				5,621,664
Costs capitalized subsequent to acquisition, Building and Improvements				414,781
Gross amount at which carried at close of period, Land				2,065,206
Gross amount at which carried at close of period, Buildings and Improvements				6,036,445
Gross amount at which carried at close of period, Total	$ 8,101,651	$ 8,329,475	$ 7,849,093	8,101,651
Accumulated depreciation and amortization	(644,639)	(487,945)	(318,161)	(644,639)
Costs capitalized subsequent to acquisition, Building and Improvements, other				4,572
Gross amount at which carried at close of period, Buildings and Improvements, other				4,572
Gross amount at which carried at close of period, other				4,572
Accumulated depreciation and amortization, other	$ (1,332)
Date acquired, other	Nov. 24, 2014
Real Estate:
Beginning balance	$ 8,329,475	7,849,093	7,652,117
Acquisitions		484,916	504,684
Buildings and improvements	146,378	82,862	116,038
Assets held for sale			(412,315)
Real estate impairment loss	(46,000)
Assets sold and written-off	(328,202)	(87,396)	(11,431)
Ending balance	8,101,651	8,329,475	7,849,093
Accumulated Depreciation:
Beginning balance	487,945	318,161	243,089
Additions charged to expense	188,871	182,732	168,847
Accumulated depreciation related to assets held for sale			(82,344)
Accumulated depreciation related to assets sold and written-off	(32,177)	(12,948)	(11,431)
Ending balance	$ 644,639	$ 487,945	$ 318,161
Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed, other	5 years
Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed, other	40 years
1633 Broadway [Member]
Real Estate And Accumulated Depreciation [Line Items]
Encumbrances				1,046,800
Initial cost to company, Land				502,846
Initial cost to company, Building and Improvements				1,398,341
Costs capitalized subsequent to acquisition, Building and Improvements				125,286
Gross amount at which carried at close of period, Land				502,846
Gross amount at which carried at close of period, Buildings and Improvements				1,523,627
Gross amount at which carried at close of period, Total	$ 2,026,473			2,026,473
Accumulated depreciation and amortization	$ (168,325)			(168,325)
Date of construction	Dec. 31, 1971
Date acquired	Nov. 24, 2014
Real Estate:
Ending balance	$ 2,026,473
Accumulated Depreciation:
Ending balance	$ 168,325
1633 Broadway [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
1633 Broadway [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
1301 Avenue of Americas [Member]
Real Estate And Accumulated Depreciation [Line Items]
Encumbrances				850,000
Initial cost to company, Land				406,039
Initial cost to company, Building and Improvements				1,051,697
Costs capitalized subsequent to acquisition, Building and Improvements				91,556
Gross amount at which carried at close of period, Land				406,039
Gross amount at which carried at close of period, Buildings and Improvements				1,143,253
Gross amount at which carried at close of period, Total	$ 1,549,292			1,549,292
Accumulated depreciation and amortization	$ (128,742)			(128,742)
Date of construction	Dec. 31, 1963
Date acquired	Nov. 24, 2014
Real Estate:
Ending balance	$ 1,549,292
Accumulated Depreciation:
Ending balance	$ 128,742
1301 Avenue of Americas [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
1301 Avenue of Americas [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
31 West 52nd Street [Member]
Real Estate And Accumulated Depreciation [Line Items]
Encumbrances				500,000
Initial cost to company, Land				221,318
Initial cost to company, Building and Improvements				604,994
Costs capitalized subsequent to acquisition, Building and Improvements				44,739
Gross amount at which carried at close of period, Land				221,318
Gross amount at which carried at close of period, Buildings and Improvements				649,733
Gross amount at which carried at close of period, Total	$ 871,051			871,051
Accumulated depreciation and amortization	$ (68,588)			(68,588)
Date of construction	Dec. 31, 1987
Date acquired	Nov. 24, 2014
Real Estate:
Ending balance	$ 871,051
Accumulated Depreciation:
Ending balance	$ 68,588
31 West 52nd Street [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
31 West 52nd Street [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
1325 Avenue of the Americas [Member]
Real Estate And Accumulated Depreciation [Line Items]
Initial cost to company, Land				174,688
Initial cost to company, Building and Improvements				370,553
Costs capitalized subsequent to acquisition, Building and Improvements				30,395
Gross amount at which carried at close of period, Land				174,688
Gross amount at which carried at close of period, Buildings and Improvements				400,948
Gross amount at which carried at close of period, Total	$ 575,636			575,636
Accumulated depreciation and amortization	$ (45,238)			(45,238)
Date of construction	Dec. 31, 1989
Date acquired	Nov. 24, 2014
Real Estate:
Ending balance	$ 575,636
Accumulated Depreciation:
Ending balance	$ 45,238
1325 Avenue of the Americas [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
1325 Avenue of the Americas [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
900 Third Avenue [Member]
Real Estate And Accumulated Depreciation [Line Items]
Initial cost to company, Land				103,741
Initial cost to company, Building and Improvements				296,031
Costs capitalized subsequent to acquisition, Building and Improvements				14,745
Gross amount at which carried at close of period, Land				103,741
Gross amount at which carried at close of period, Buildings and Improvements				310,776
Gross amount at which carried at close of period, Total	$ 414,517			414,517
Accumulated depreciation and amortization	$ (38,314)			(38,314)
Date of construction	Dec. 31, 1983
Date acquired	Nov. 24, 2014
Real Estate:
Ending balance	$ 414,517
Accumulated Depreciation:
Ending balance	$ 38,314
900 Third Avenue [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
900 Third Avenue [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
Total New York [Member]
Real Estate And Accumulated Depreciation [Line Items]
Encumbrances				2,396,800
Initial cost to company, Land				1,408,632
Initial cost to company, Building and Improvements				3,721,616
Costs capitalized subsequent to acquisition, Building and Improvements				306,721
Gross amount at which carried at close of period, Land				1,408,632
Gross amount at which carried at close of period, Buildings and Improvements				4,028,337
Gross amount at which carried at close of period, Total	$ 5,436,969			5,436,969
Accumulated depreciation and amortization	(449,207)			(449,207)
Real Estate:
Ending balance	5,436,969
Accumulated Depreciation:
Ending balance	449,207
Liberty Place [Member]
Real Estate And Accumulated Depreciation [Line Items]
Initial cost to company, Land				46,401
Initial cost to company, Building and Improvements				96,422
Costs capitalized subsequent to acquisition, Building and Improvements				12,741
Gross amount at which carried at close of period, Land				46,401
Gross amount at which carried at close of period, Buildings and Improvements				109,163
Gross amount at which carried at close of period, Total	155,564			155,564
Accumulated depreciation and amortization	$ (14,233)			(14,233)
Date of construction	Dec. 31, 1993
Date acquired	Nov. 24, 2014
Real Estate:
Ending balance	$ 155,564
Accumulated Depreciation:
Ending balance	$ 14,233
Liberty Place [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
Liberty Place [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
1899 Pennsylvania Avenue [Member]
Real Estate And Accumulated Depreciation [Line Items]
Initial cost to company, Land				52,568
Initial cost to company, Building and Improvements				94,874
Costs capitalized subsequent to acquisition, Building and Improvements				4,207
Gross amount at which carried at close of period, Land				52,568
Gross amount at which carried at close of period, Buildings and Improvements				99,081
Gross amount at which carried at close of period, Total	$ 151,649			151,649
Accumulated depreciation and amortization	$ (12,432)			(12,432)
Date of construction	Dec. 31, 1915
Date acquired	Nov. 24, 2014
Real Estate:
Ending balance	$ 151,649
Accumulated Depreciation:
Ending balance	$ 12,432
1899 Pennsylvania Avenue [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
1899 Pennsylvania Avenue [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
Total Washington, D.C. [Member]
Real Estate And Accumulated Depreciation [Line Items]
Initial cost to company, Land				98,969
Initial cost to company, Building and Improvements				191,296
Costs capitalized subsequent to acquisition, Building and Improvements				16,948
Gross amount at which carried at close of period, Land				98,969
Gross amount at which carried at close of period, Buildings and Improvements				208,244
Gross amount at which carried at close of period, Total	$ 307,213			307,213
Accumulated depreciation and amortization	(26,665)			(26,665)
Real Estate:
Ending balance	307,213
Accumulated Depreciation:
Ending balance	26,665
One Market Plaza [Member]
Real Estate And Accumulated Depreciation [Line Items]
Encumbrances				975,000
Initial cost to company, Land				288,743
Initial cost to company, Building and Improvements				988,014
Costs capitalized subsequent to acquisition, Building and Improvements				70,757
Gross amount at which carried at close of period, Land				288,743
Gross amount at which carried at close of period, Buildings and Improvements				1,058,771
Gross amount at which carried at close of period, Total	1,347,514			1,347,514
Accumulated depreciation and amortization	$ (125,743)			(125,743)
Date of construction	Dec. 31, 1976
Date acquired	Nov. 24, 2014
Real Estate:
Ending balance	$ 1,347,514
Accumulated Depreciation:
Ending balance	$ 125,743
One Market Plaza [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
One Market Plaza [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
One Front Street [Member]
Real Estate And Accumulated Depreciation [Line Items]
Initial cost to company, Land				127,765
Initial cost to company, Building and Improvements				376,919
Costs capitalized subsequent to acquisition, Building and Improvements				7,731
Gross amount at which carried at close of period, Land				127,765
Gross amount at which carried at close of period, Buildings and Improvements				384,650
Gross amount at which carried at close of period, Total	$ 512,415			512,415
Accumulated depreciation and amortization	$ (24,824)			(24,824)
Date of construction	Dec. 31, 1979
Date acquired	Dec. 31, 2016
Real Estate:
Ending balance	$ 512,415
Accumulated Depreciation:
Ending balance	$ 24,824
One Front Street [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
One Front Street [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
50 Beale Street [Member]
Real Estate And Accumulated Depreciation [Line Items]
Encumbrances				228,000
Initial cost to company, Land				141,097
Initial cost to company, Building and Improvements				343,819
Costs capitalized subsequent to acquisition, Building and Improvements				8,052
Gross amount at which carried at close of period, Land				141,097
Gross amount at which carried at close of period, Buildings and Improvements				351,871
Gross amount at which carried at close of period, Total	$ 492,968			492,968
Accumulated depreciation and amortization	$ (16,868)			(16,868)
Date of construction	Dec. 31, 1968
Date acquired	Jul. 17, 2017
Real Estate:
Ending balance	$ 492,968
Accumulated Depreciation:
Ending balance	$ 16,868
50 Beale Street [Member] | Minimum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	5 years
50 Beale Street [Member] | Maximum [Member]
Real Estate And Accumulated Depreciation [Line Items]
Life on which depreciation in latest income statement is computed	40 years
Total San Francisco [Member]
Real Estate And Accumulated Depreciation [Line Items]
Encumbrances				1,203,000
Initial cost to company, Land				557,605
Initial cost to company, Building and Improvements				1,708,752
Costs capitalized subsequent to acquisition, Building and Improvements				86,540
Gross amount at which carried at close of period, Land				557,605
Gross amount at which carried at close of period, Buildings and Improvements				1,795,292
Gross amount at which carried at close of period, Total	$ 2,352,897			2,352,897
Accumulated depreciation and amortization	(167,435)			$ (167,435)
Real Estate:
Ending balance	2,352,897
Accumulated Depreciation:
Ending balance	$ 167,435