Segment Information - Summary of Third-party Asset Management and Real Estate Services (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Third-party real estate services revenue, excluding reimbursements	$ 13,279	$ 19,526	$ 42,463	$ 48,823
Reimbursements revenue	13,708	15,061	41,407	42,942
Third-party real estate services revenue, including reimbursements	26,987	34,587	83,870	91,765
Third-party real estate services expenses	28,207	29,809	86,260	86,585
Third-party real estate services revenue less expenses	(1,220)	4,778	(2,390)	5,180
Property management fees
Third-party real estate services revenue, excluding reimbursements	4,694	5,758	15,453	16,873
Asset management fees
Third-party real estate services revenue, excluding reimbursements	2,301	3,577	7,400	10,612
Leasing fees
Third-party real estate services revenue, excluding reimbursements	1,086	2,033	3,627	5,331
Development fees
Third-party real estate services revenue, excluding reimbursements	2,614	6,783	8,474	10,912
Construction management fees
Third-party real estate services revenue, excluding reimbursements	584	370	2,057	1,469
Other service revenue
Third-party real estate services revenue, excluding reimbursements	$ 2,000	$ 1,005	$ 5,452	$ 3,626