Segments - Schedule of NOI for Each Reportable Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020		Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Property-related revenues		$ 176,068	$ 168,455		$ 350,564	$ 349,773
Property-related operating expenses		(64,072)	(65,712)		(130,690)	(134,177)
NOI from unconsolidated joint ventures		10,557	10,376		20,883	23,768
NOI	[1]	122,553	113,119		240,757	239,364
New York [Member]
Segment Reporting Information [Line Items]
Property-related revenues		108,191	110,679		220,028	232,256
Property-related operating expenses		(45,801)	(47,213)		(94,825)	(96,242)
NOI from unconsolidated joint ventures		2,749	2,680		5,570	5,624
NOI	[1]	65,139	66,146		130,773	141,638
San Francisco [Member]
Segment Reporting Information [Line Items]
Property-related revenues		68,674	54,827		132,146	111,494
Property-related operating expenses		(17,067)	(16,054)		(34,005)	(32,973)
NOI from unconsolidated joint ventures		7,852	9,165		15,389	19,547
NOI	[1]	59,459	47,938		113,530	98,068
Other [Member]
Segment Reporting Information [Line Items]
Property-related revenues		(797)	2,949	[2]	(1,610)	6,023	[2]
Property-related operating expenses		(1,204)	(2,445)	[2]	(1,860)	(4,962)	[2]
NOI from unconsolidated joint ventures		(44)	(1,469)	[2]	(76)	(1,403)	[2]
NOI	[1]	$ (2,045)	$ (965)	[2]	$ (3,546)	$ (342)	[2]

[1] NOI is used to measure the operating performance of our properties. NOI consists of rental revenue (which includes property rentals, tenant reimbursements and lease termination income) and certain other property-related revenue less operating expenses (which includes property-related expenses such as cleaning, security, repairs and maintenance, utilities, property administration and real estate taxes). We use NOI internally as a performance measure and believe it provides useful information to investors regarding our financial condition and results of operations because it reflects only those income and expense items that are incurred at the property level. Other real estate companies may use different methodologies for calculating NOI and, accordingly, our presentation of NOI may not be comparable to other real estate companies.

[2] NOI for the three and six months ended June 30, 2020 includes NOI from discontinued operations. See Note 3, Discontinued Operations.