Segments - Schedule of NOI for Each Reportable Segment Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Property-related revenues	$ 746,436	$ 740,332	$ 694,755
Property-related operating expenses	(274,836)	(274,078)	(266,136)
NOI from unconsolidated joint ventures	22,409	20,730	19,643
NOI	494,009	486,984	448,262
New York [Member]
Segment Reporting Information [Line Items]
Property-related revenues	482,648	468,013	430,548
Property-related operating expenses	(191,211)	(188,008)	(180,855)
NOI from unconsolidated joint ventures	13,151	20,395	19,143
NOI	304,588	300,400	268,836
San Francisco [Member]
Segment Reporting Information [Line Items]
Property-related revenues	238,808	222,071	191,677
Property-related operating expenses	(69,815)	(60,043)	(50,906)
NOI from unconsolidated joint ventures	9,065
NOI	178,058	162,028	140,771
Washington, D.C. [Member]
Segment Reporting Information [Line Items]
Property-related revenues	25,426	51,290	72,143
Property-related operating expenses	(10,134)	(19,381)	(27,342)
NOI	15,292	31,909	44,801
Other [Member]
Segment Reporting Information [Line Items]
Property-related revenues	(446)	(1,042)	387
Property-related operating expenses	(3,676)	(6,646)	(7,033)
NOI from unconsolidated joint ventures	193	335	500
NOI	$ (3,929)	$ (7,353)	$ (6,146)