Equity and Employee Stock Plans - Schedule of Stock Option Activity (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Number Of Options
Outstanding, beginning balance (in shares) | shares	9,435,349
Options granted (in shares) | shares	150,000
Options exercised (in shares) | shares	(1,397,074)
Options forfeited (in shares) | shares	(81,826)
Options canceled (in shares) | shares	(4,278)
Outstanding, ending balance (in shares) | shares	8,102,171	9,435,349
Options exercisable at period end (in shares) | shares	7,100,240
Weighted- Average Exercise Price
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 6.48
Options granted (in dollars per share) | $ / shares	27.50
Options exercised (in dollars per share) | $ / shares	5.49
Options forfeited (in dollars per share) | $ / shares	9.16
Options canceled (in dollars per share) | $ / shares	8.22
Outstanding, ending balance (in dollars per share) | $ / shares	7.01	$ 6.48
Options exercisable at period end (in dollars per share) | $ / shares	$ 6.30
Weighted-Average Remaining Contractual Life (Years)
Weighted average remaining contractual life outstanding	5 years 7 months 2 days	6 years 21 days
Weighted average remaining contractual life exercisable	5 years 3 months 25 days
Aggregate Intrinsic Value
Options outstanding, Aggregate intrinsic value | $	$ 81,204	$ 74,669
Options exercisable, Aggregate intrinsic value | $	$ 74,839