Segments - Schedule of NOI for Each Reportable Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020		Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Property-related revenues		$ 172,570	$ 171,263		$ 523,134	$ 521,036
Property-related operating expenses		(67,131)	(69,349)		(197,821)	(203,526)
NOI from unconsolidated joint ventures		16,214	12,935		37,097	36,703
NOI	[1]	117,066	114,849		357,823	354,213
One Steuart Lane [Member]
Segment Reporting Information [Line Items]
NOI from unconsolidated joint ventures		(4,587)			(4,587)
New York [Member]
Segment Reporting Information [Line Items]
Property-related revenues		109,842	106,287		329,870	338,543
Property-related operating expenses		(47,545)	(49,072)		(142,370)	(145,314)
NOI from unconsolidated joint ventures		2,875	3,116		8,445	8,740
NOI	[1]	65,172	60,331		195,945	201,969
San Francisco [Member]
Segment Reporting Information [Line Items]
Property-related revenues		63,527	62,086		195,673	173,580
Property-related operating expenses		(18,646)	(17,825)		(52,651)	(50,798)
NOI from unconsolidated joint ventures		8,665	10,019		24,054	29,566
NOI	[1]	53,546	54,280		167,076	152,348
Other [Member]
Segment Reporting Information [Line Items]
Property-related revenues		(799)	2,890	[2]	(2,409)	8,913	[2]
Property-related operating expenses		(940)	(2,452)	[2]	(2,800)	(7,414)	[2]
NOI from unconsolidated joint ventures		4,674	(200)	[2]	4,598	(1,603)	[2]
NOI	[1]	(1,652)	$ 238	[2]	(5,198)	$ (104)	[2]
Other [Member] | One Steuart Lane [Member]
Segment Reporting Information [Line Items]
NOI from unconsolidated joint ventures		$ (4,587)			$ (4,587)

[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 nine months ended September 30, 2020 includes NOI from discontinued operations. See Note 3, Discontinued Operations.