Costs and Estimated Earnings on Uncompleted Contracts - Costs and Estimated Earnings on Uncompleted Contracts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Costs In Excess Of Billings On Uncompleted Contracts Or Programs [Abstract]
Costs incurred on uncompleted contracts	$ 169,665	$ 186,609
Estimated earnings	61,556	77,709
Total costs and estimated earnings on uncompleted contracts, gross	231,221	264,318
Less billings to date	(217,743)	(261,280)
Total costs and estimated earnings on uncompleted contracts, net	13,478	3,038
Included in the accompanying consolidated balance sheets under the following captions:
Costs and estimated earnings in excess of billings on uncompleted contracts	33,947	38,123
Billings in excess of costs and estimated earnings on uncompleted contracts	(20,469)	(35,085)
Total costs and estimated earnings on uncompleted contracts, net	$ 13,478	$ 3,038