Stockholders' Equity - Stock Option Activity (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Number of shares
Beginning balance outstanding (in shares) | shares	2,282,636
Granted (in shares) | shares	1,484,352
Exercised (in shares) | shares	(252,773)
Forfeited (in shares) | shares	(55,768)
Ending balance outstanding (in shares) | shares	3,458,447
Vested and expected to vest (in shares) | shares	3,449,778
Exercisable (in shares) | shares	1,861,890
Weighted average exercise price
Beginning balance outstanding (in dollars per share) | $ / shares	$ 5.06
Granted (in dollars per share) | $ / shares	17.00
Exercised (in dollars per share) | $ / shares	4.53
Forfeited (in dollars per share) | $ / shares	7.26
Ending balance outstanding (in dollars per share) | $ / shares	10.19
Vested and expected to vest (in dollars per share) | $ / shares	10.21
Exercisable (in dollars per share) | $ / shares	$ 7.23
Weighted average contractual term
Outstanding (in years)	8 years
Vested and expected to vest (in years)	8 years
Exercisable (in years)	6 years 6 months
Aggregate intrinsic value
Outstanding (in dollars) | $	$ 322,229,820
Vested and expected to vest (in dollars) | $	321,347,251
Exercisable (in dollars) | $	$ 178,992,676