Segments - Schedule of NOI for Each Reportable Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Property-related revenues	$ 184,370	$ 186,010	$ 370,163	$ 366,816
Property-related operating expenses	(67,572)	(67,646)	(135,953)	(136,624)
NOI from unconsolidated joint ventures	4,185	4,569	9,596	9,309
NOI	120,983	122,933	243,806	239,501
New York [Member]
Segment Reporting Information [Line Items]
Property-related revenues	118,741	115,536	239,837	229,181
Property-related operating expenses	(46,504)	(45,292)	(94,607)	(92,453)
NOI from unconsolidated joint ventures	2,886	4,493	7,543	9,158
NOI	75,123	74,737	152,773	145,886
San Francisco [Member]
Segment Reporting Information [Line Items]
Property-related revenues	58,431	55,344	115,615	107,243
Property-related operating expenses	(17,479)	(15,048)	(33,825)	(29,164)
NOI from unconsolidated joint ventures	1,213		1,913
NOI	42,165	40,296	83,703	78,079
Washington, D.C. [Member]
Segment Reporting Information [Line Items]
Property-related revenues	7,240	15,435	14,643	30,884
Property-related operating expenses	(2,836)	(5,736)	(5,756)	(11,581)
NOI	4,404	9,699	8,887	19,303
Other [Member]
Segment Reporting Information [Line Items]
Property-related revenues	(42)	(305)	68	(492)
Property-related operating expenses	(753)	(1,570)	(1,765)	(3,426)
NOI from unconsolidated joint ventures	86	76	140	151
NOI	$ (709)	$ (1,799)	$ (1,557)	$ (3,767)