Segments - Schedule of NOI for Each Reportable Segment Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Property-related revenues	$ 740,332	$ 694,755	$ 666,410
Property-related operating expenses	(274,078)	(266,136)	(250,040)
NOI from unconsolidated joint ventures	20,730	19,643	17,195
NOI	486,984	448,262	433,565
New York [Member]
Segment Reporting Information [Line Items]
Property-related revenues	468,013	430,548	449,794
Property-related operating expenses	(188,008)	(180,855)	(176,445)
NOI from unconsolidated joint ventures	20,395	19,143	16,874
NOI	300,400	268,836	290,223
Washington, D.C. [Member]
Segment Reporting Information [Line Items]
Property-related revenues	51,290	72,143	86,389
Property-related operating expenses	(19,381)	(27,342)	(32,721)
NOI	31,909	44,801	53,668
San Francisco [Member]
Segment Reporting Information [Line Items]
Property-related revenues	222,071	191,677	127,813
Property-related operating expenses	(60,043)	(50,906)	(30,889)
NOI	162,028	140,771	96,924
Other [Member]
Segment Reporting Information [Line Items]
Property-related revenues	(1,042)	387	2,414
Property-related operating expenses	(6,646)	(7,033)	(9,985)
NOI from unconsolidated joint ventures	335	500	321
NOI	$ (7,353)	$ (6,146)	$ (7,250)