Construction Contracts - Summary of Costs in Excess of Billings and Billings in Excess of Costs (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Construction contract costs and estimated earnings in excess of billings
Beginning balance	$ 138	$ 249
Transferred to receivables	(665)	(468)
Construction contract costs and estimated earnings not billed during the period	370	215
Changes due to cumulative catch-up adjustment arising from changes in the estimate of the stage of completion	527	219
Ending balance	370	215
Billings in excess of construction contract costs and estimated earnings
Beginning balance	6,088	5,306
Revenue recognized that was included in the balance at the beginning of the period	(6,088)	(5,306)
Increases due to new billings, excluding amounts recognized as revenue during the period	3,791	7,237
Changes due to cumulative catch-up adjustment arising from changes in the estimate of the stage of completion	(1,117)	(152)
Ending balance	$ 2,674	$ 7,085