Acquisitions - Additional Information (Details) ft² in Thousands	Aug. 16, 2019 USD ($) ft² Building	Sep. 30, 2019 ft²
Business Acquisition [Line Items]
Area of office and retail properties		12,400
Market Center [Member]
Business Acquisition [Line Items]
Number of buildings acquired | Building	2
Area of office and retail properties	753
Purchase price of real estate | $	$ 722,000,000
Market Center [Member] | Other Assets [Member]
Business Acquisition [Line Items]
Deposit for acquisition | $	$ 25,000,000
555 Market Street [Member]
Business Acquisition [Line Items]
Area of office and retail properties	280
575 Market Street [Member]
Business Acquisition [Line Items]
Area of office and retail properties	473