Investments in Unconsolidated Joint Ventures - Additional Information (Details)	Mar. 29, 2019 USD ($)	Feb. 07, 2019 USD ($) ft² Extensions	Jun. 30, 2019 ft²
Schedule Of Equity Method Investments [Line Items]
Area of office and retail properties | ft²			12,200,000
RDF [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage in residential fund	7.40%
Percentage of interest third party ownership	92.60%
One Steuart Lane [Member]
Schedule Of Equity Method Investments [Line Items]
Percentage of ownership interest in new joint venture			30.00%
Property funds, ownership percentage			2.20%
One Steuart Lane [Member] | RDF [Member]
Schedule Of Equity Method Investments [Line Items]
Percentage of interest acquired	5.00%
Additional interest acquired amount	$ 9,339,000
Property funds, ownership percentage	30.00%
Joint Venture
Schedule Of Equity Method Investments [Line Items]
Percentage of ownership interest in joint venture held by co-venturer	70.00%
111 Sutter Street [Member]
Schedule Of Equity Method Investments [Line Items]
Area of office and retail properties | ft²		293,000
Business combination, consideration transferred		$ 227,000,000
Percentage of ownership interest in new joint venture		49.00%
Percentage of ownership interest in joint venture held by co-venturer		51.00%
Mortgage financing amount		$ 138,200,000
Debt instrument, term		4 years
Debt instrument number of extensions | Extensions		3
Debt instrument term of extension		1 year
111 Sutter Street [Member] | London Interbank Offered Rate (LIBOR) [Member]
Schedule Of Equity Method Investments [Line Items]
Mortgage financing loan, interest only basis points at LIBOR		2.15%