Equity Awards - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Number of shares, outstanding, beginning balance (in shares)	3,369,732	5,818,435
Number of shares, granted (in shares)	0	616,720
Number of shares, exercised (in shares)	(1,461,712)	(2,970,914)
Number of shares, canceled (in shares)	(97,440)	(94,509)
Number of shares, outstanding, ending balance (in shares)	1,810,580	3,369,732	5,818,435
Number of shares, vested and expected to vest (in shares)	1,804,158
Number of shares, vested and exercisable (in shares)	1,319,851
Weighted- Average Exercise Price
Weighted-average exercise price, outstanding, beginning balance (in USD per share)	$ 38.43	$ 20.57
Weighted-average exercise price, granted (in USD per share)		86.33
Weighted-average exercise price, exercised (in USD per share)	26.23	12.44
Weighted-average exercise price, canceled (in USD per share)	70.52	68.88
Weighted-average exercise price, outstanding, ending balance (in USD per share)	46.55	$ 38.43	$ 20.57
Weighted-average exercise price, vested and expected to vest (in USD per share)	46.45
Weighted-average exercise price, vested and exercisable (in USD per share)	$ 32.90
Weighted-average remaining contractual life (in years)	5 years 3 months 18 days
Weighted-average remaining contractual term, vested and expected to vest (in years)	5 years 3 months 14 days
Weighted-average remaining contractual term, vested and exercisable (in years)	4 years 3 months 18 days
Total intrinsic value of options exercised	$ 204,337	$ 277,670	$ 157,800
Aggregate intrinsic value, outstanding	238,092
Aggregate intrinsic value, vested and expected to vest	237,425
Aggregate intrinsic value, vested and exercisable	$ 191,580