Stock-Based Compensation - Schedule of Additional Information on Unvested Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average remaining contractual term (in years)	4 years 6 months 25 days	4 years 9 months 18 days
Aggregate intrinsic value	$ 126,467	$ 236,546
Unvested Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding (in shares)	3,721,832	3,724,570
Weighted-average exercise price (in dollars per share)	$ 88.37	$ 80.39
Weighted-average remaining contractual term (in years)	5 years 7 months 13 days	6 years 14 days
Aggregate intrinsic value	$ 31,941	$ 92,611