Stock Based Compensation - Costs Related to Company's Stock-Based Compensation Plan (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expenses	$ 5,027	$ 4,484	$ 4,450	$ 5,809	$ 3,768	$ 4,471	$ 3,553	$ 4,255	$ 19,770	$ 16,047	$ 11,011
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expenses									3,664	2,895	2,290
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expenses									8,372	6,077	4,350
Selling and marketing expenses
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expenses									$ 7,734	$ 7,075	$ 4,371