Revenue Recognition - Schedule of Net Under (Over) Billings (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Contractors [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts (contract assets)	$ 18,101	$ 6,182
Billings in excess of costs and estimated earnings on uncompleted contracts (contract liabilities)	(4,637)	(4,376)
Net under (over) billings	$ 13,464	$ 1,806