Stockholders' Equity - Stock-Based Compensation Expense Related to Grants of Employee Stock Options, Restricted Stock Units (RSUs) and Performance and Market Based Awards (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 44,600,000	$ 38,800,000	$ 125,000,000.0	$ 84,900,000
Cost of Revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	800,000	600,000	2,000,000.0	1,500,000
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	29,900,000	25,400,000	83,000,000.0	48,600,000
Sales and Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4,400,000	4,000,000.0	13,000,000.0	11,000,000.0
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 9,500,000	$ 8,800,000	$ 27,000,000.0	$ 23,800,000