Stock-Based Compensation - Schedule of Additional Information on Unvested Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average remaining contractual term (in years)	4 years 9 months 18 days	4 years 9 months 7 days
Aggregate intrinsic value	$ 236,546	$ 114,161
Unvested Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding (in shares)	3,724,570	3,810,675
Weighted-average exercise price (in dollars per share)	$ 80.39	$ 73.78
Weighted-average remaining contractual term (in years)	6 years 14 days	6 years 5 months 12 days
Aggregate intrinsic value	$ 92,611	$ 24,344