Stockholders' Equity - Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares
Number of shares
Beginning balance outstanding (in shares) | shares	3,458,447
Granted (in shares) | shares	566,815
Exercised (in shares) | shares	(60,186)
Forfeited (in shares) | shares	(2,343)
Ending balance outstanding (in shares) | shares	3,962,733
Vested and expected to vest (in shares) | shares	3,954,064
Exercisable (in shares) | shares	1,958,757
Weighted average exercise price
Beginning balance outstanding (in dollars per share) | $ / shares	$ 10.19
Granted (in dollars per share) | $ / shares	51.12
Exercised (in dollars per share) | $ / shares	10.46
Forfeited (in dollars per share) | $ / shares	13.98
Ending balance outstanding (in dollars per share) | $ / shares	16.04
Vested and expected to vest (in dollars per share) | $ / shares	16.07
Exercisable (in dollars per share) | $ / shares	$ 7.48
Weighted average contractual term
Outstanding (in years)	8 years
Vested and expected to vest (in years)	8 years
Exercisable (in years)	6 years 4 months 24 days
Aggregate intrinsic value
Outstanding (in dollars) | $	$ 171,744,639
Vested and expected to vest (in dollars) | $	171,248,106
Exercisable (in dollars) | $	$ 100,572,453