Equity Awards - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2020
Number of Shares
Outstanding, beginning balance (in shares)	651,000	994,000	1,154,000	1,154,000
Exercised (in shares)	(46,000)	(343,000)	(149,000)
Canceled (in shares)			(11,000)
Outstanding, ending balance (in shares)	604,000	651,000	994,000	604,000
Vested and expected to vest (in shares)	580,000			580,000
Vested and exercisable (in shares)	425,000			425,000
Weighted- Average Exercise Price Per Share
Outstanding, beginning balance (in dollars per share)	$ 92.87	$ 85.08	$ 77.70	$ 77.70
Exercised (in dollars per share)	25.03	70.33	28.47
Canceled (in dollars per share)			75.77
Outstanding, ending balance (in dollars per share)	98.16	$ 92.87	$ 85.08	98.16
Vested and expected to vest (in dollars per share)	91.47			91.47
Vested and exercisable (in dollars per share)	$ 34.83			$ 34.83
Weighted-average remaining contractual term, outstanding				4 years 7 months 6 days
Weighted-average remaining contractual term, vested and expected to vest				4 years 4 months 24 days
Weighted-average remaining contractual term, vested and exercisable				2 years 8 months 12 days
Aggregate intrinsic value, exercised	$ 20,233	$ 95,041	$ 44,465
Aggregate intrinsic value, outstanding	233,515			$ 233,515
Aggregate intrinsic value, vested and expected to vest	228,345			228,345
Aggregate intrinsic value, vested and exercisable	$ 191,110			$ 191,110