Stock-Based Compensation Expense - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 10,430	$ 7,350	$ 19,064	$ 13,575
Cost of Revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	718	469	1,291	843
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	4,054	2,850	7,228	5,416
Sales and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	2,942	2,055	5,406	3,618
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 2,716	$ 1,976	$ 5,139	$ 3,698