Revenue Recognition - Summary of Information About the Company's Contract Balances (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Revenue From Contract With Customer [Abstract]
Costs in excess of billings	$ 2,827	$ 1,310	$ 1,815
Billings in excess of costs	$ 6,136	$ 7,204	$ 5,953