Segments - Schedule of NOI for Each Reportable Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Property-related revenues	$ 180,806	$ 171,680
Property-related operating expenses	(68,978)	(65,971)
NOI from unconsolidated joint ventures	4,740	4,823
NOI	116,568	110,532
New York [Member]
Segment Reporting Information [Line Items]
Property-related revenues	113,645	105,324
Property-related operating expenses	(47,161)	(44,759)
NOI from unconsolidated joint ventures	4,665	4,753
NOI	71,149	65,318
Washington, D.C. [Member]
Segment Reporting Information [Line Items]
Property-related revenues	15,449	23,787
Property-related operating expenses	(5,845)	(8,924)
NOI	9,604	14,863
San Francisco [Member]
Segment Reporting Information [Line Items]
Property-related revenues	51,899	41,939
Property-related operating expenses	(14,116)	(10,605)
NOI	37,783	31,334
Other [Member]
Segment Reporting Information [Line Items]
Property-related revenues	(187)	630
Property-related operating expenses	(1,856)	(1,683)
NOI from unconsolidated joint ventures	75	70
NOI	$ (1,968)	$ (983)