Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Beginning balance (in shares)	2,641,198	3,001,929
Options granted (in shares)	638,983	100,080
Options exercised (in shares)	(444,924)	(395,117)
Options canceled and forfeited (in shares)	(116,286)	(65,694)
Ending balance (in shares)	2,718,971	2,641,198
Options vested and exercisable (in shares)	2,126,781
Options vested and expected to vest (in shares)	2,652,883
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 4.27	$ 4.15
Options granted (in dollars per share)	20.89	8.88
Options exercised (in dollars per share)	3.36	4.08
Options canceled and forfeited (in dollars per share)	11.30	4.81
Ending balance (in dollars per share)	8.02	$ 4.27
Options vested and exercisable (in dollars per share)	5.32
Options vested and expected to vest (in dollars per share)	$ 7.80
Weighted-Average Remaining Contractual Life and Aggregate Intrinsic Value
Weighted-average remaining contractual life, options outstanding (in years)	6 years 9 months 29 days
Weighted-average remaining contractual life, options vested and exercisable (in years)	6 years 3 months 8 days
Weighted-average remaining contractual life, options vested and expected to vest (in years)	6 years 9 months 3 days
Aggregate intrinsic value, options outstanding	$ 36,872
Aggregate intrinsic value, options vested and exercisable	34,463
Aggregate intrinsic value, options vested and expected to vest	$ 36,540