Segments - Additional information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information
General contracting and real estate services expenses									$ 101,538	$ 73,628	$ 186,590
General contracting and real estate services revenues
Segment Reporting Information
General contracting and real estate services revenues	$ 39,741	$ 27,638	$ 21,444	$ 17,036	$ 12,705	$ 19,950	$ 20,654	$ 23,050	105,859	76,359	194,034
General contracting and real estate services revenues | General contracting and real estate services | Intersegment Eliminations
Segment Reporting Information
General contracting and real estate services revenues									99,900	134,400	51,500
General contracting and real estate services expenses									$ 99,000	$ 133,400	$ 51,000