Stock Incentive Plans - Summary of Stock Option Activity Under 2006 and 2016 Plans, Including Grants To Nonemployees (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2019
Options Outstanding
Beginning balance (in shares)	2,094,137	2,601,181	2,977,218
Options granted (in shares)	20,010	366,928	465,271
Options exercised (in shares)	(540,307)	(798,424)	(827,556)
Options forfeited (in shares)	(70,593)	(75,548)	(13,752)
Ending balance (in shares)	1,503,247	2,094,137	2,601,181	2,977,218
Options exercisable (in shares)					1,147,525
Options vested and expected to vest (in shares)					1,487,867
Weighted Average Exercise Price Per Share [Abstract]
Beginning balance (in USD per share)	$ 23.20	$ 12.24	$ 6.16
Options granted (in USD per share)	82.77	68.32	36.76
Options exercised (in USD per share)	9.59	7.19	4.11
Options forfeited (in USD per share)	54.54	34.30	14.43
Ending balance (in USD per share)	$ 27.40	$ 23.20	$ 12.24	$ 6.16
Options exercisable (in USD per share)					$ 19.64
Options vested and expected to vest (in USD per share)					$ 27.07
Weighted Average Remaining Contractual Life (Years) [Abstract]
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	6 years 5 months 4 days	7 years 7 days	7 years 2 months 1 day	6 years 11 months 4 days
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	6 years 5 months 4 days	7 years 7 days	7 years 2 months 1 day	6 years 11 months 4 days
Options exercisable	6 years 7 days
Options vested and expected to vest	6 years 4 months 28 days
Aggregate Intrinsic Value (in thousands)
Beginning balance	$ 97,976	$ 113,958	$ 70,979
Ending balance	$ 97,976	$ 113,958	$ 70,979	$ 70,979	$ 62,401
Options exercisable					55,919
Options vested and expected to vest					$ 62,220