Accounts Receivable, Net - Accounts Receivables Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts Receivable Net Current [Abstract]
Trade accounts receivable	$ 132,880	$ 118,916
Unbilled revenue, at net realizable value	55,982	47,351
Total accounts receivable	188,862	166,267
Allowance for doubtful accounts	(13,508)	(12,659)	$ (11,915)	$ (9,975)
Accounts receivable, net	$ 175,354	$ 153,608