Accounts Receivable - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Amount billed but not received under retainage provisions in contracts	$ 3,200	$ 2,300
Retainage receivables on contracts period	1 year
Provision for doubtful accounts	$ 848	702	$ 299
Charge-offs	$ 300	$ 200	$ 300