Segment Information - Summary of Third-party Asset Management and Real Estate Services (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Third-party real estate services revenue, excluding reimbursements	$ 13,229	$ 15,060	$ 29,184	$ 29,297
Reimbursements revenue	13,938	14,427	27,699	27,881
Third-party real estate services revenue, including reimbursements	27,167	29,487	56,883	57,178
Third-party real estate services expenses	29,239	28,710	58,053	56,776
Third-party real estate services revenue less expenses	(2,072)	777	(1,170)	402
Property management fees
Third-party real estate services revenue, excluding reimbursements	4,735	5,687	10,759	11,115
Asset management fees
Third-party real estate services revenue, excluding reimbursements	2,375	3,547	5,099	7,035
Leasing fees
Third-party real estate services revenue, excluding reimbursements	794	1,085	2,541	3,298
Development fees
Third-party real estate services revenue, excluding reimbursements	3,048	2,533	5,860	4,129
Construction management fees
Third-party real estate services revenue, excluding reimbursements	460	470	1,473	1,099
Other service revenue
Third-party real estate services revenue, excluding reimbursements	$ 1,817	$ 1,738	$ 3,452	$ 2,621