Segments - Additional information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information
General contracting and real estate services revenues	$ 32,643	$ 41,201	$ 56,671	$ 63,519	$ 50,475	$ 38,552	$ 33,200	$ 36,803	$ 194,034	$ 159,030	$ 171,268
General contracting and real estate services expenses									186,590	153,375	165,344
Non-cash stock compensation									1,323	1,082	931
General and Administrative Expenses
Segment Reporting Information
Non-cash stock compensation									900	700	700
General contracting and real estate services
Segment Reporting Information
Non-cash stock compensation									300	200	200
General contracting and real estate services | Intersegment Eliminations
Segment Reporting Information
General contracting and real estate services revenues									51,500	43,300	43,100
General contracting and real estate services expenses									$ 51,000	$ 42,700	$ 42,800