Revenue Recognition - Schedule of Net Under (Over) Billings (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Contractors [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts (contract assets)	$ 22,328	$ 22,138
Billings in excess of costs and estimated earnings on uncompleted contracts (contract liabilities)	(7,108)	(5,734)
Net under billings	$ 15,220	$ 16,404