Construction Contracts - Summary of Costs in Excess of Billings and Billings in Excess of Costs (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Construction contract costs and estimated earnings in excess of billings
Beginning balance	$ 1,358	$ 245
Transferred to receivables	(1,890)	(245)
Construction contract costs and estimated earnings not billed during the period	461	1,287
Changes due to cumulative catch-up adjustment arising from changes in the estimate of the stage of completion	532	0
Ending balance	461	1,287
Billings in excess of construction contract costs and estimated earnings
Beginning balance	3,037	3,591
Revenue recognized that was included in the balance at the beginning of the period	(3,037)	(3,591)
Increases due to new billings, excluding amounts recognized as revenue during the period	2,541	1,898
Changes due to cumulative catch-up adjustment arising from changes in the estimate of the stage of completion	(752)	(187)
Ending balance	$ 1,789	$ 1,711