Stock-Based Compensation - Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of shares
Balance at beginning of period	489,222	350,914	282,331
Granted	978,415	152,016	84,587
Exercised	(2,527)	(1,377)	(404)
Early exercised	(471)	(427)	(830)
Canceled/forfeited	(43,697)	(11,904)	(14,770)
Balance at end of period	1,420,942	489,222	350,914
Vested and expected to vest at end of period	1,317,047
Exercisable at end of period	345,881
Weighted average exercise price per share
Balance at beginning of period (in dollars per share)	$ 5.84	$ 5.81	$ 5.77
Granted ( in dollars per share)	12.51	5.93	5.93
Exercised (in dollars per share)	5.93	5.57	5.19
Early exercised (in dollars per share)	5.93	5.93	5.93
Canceled/forfeited (in dollars per share)	8.58	5.93	5.87
Balance at end of period (in dollars per share)	10.35	$ 5.84	$ 5.81
Vested and expected to vest at end of period (in dollars per share)	10.23
Exercisable at end of period (in dollars per share)	$ 5.87
Weighted average remaining contractual term
Weighted average remaining contractual term, outstanding	8 years 9 months
Weighted average remaining contractual term, Vested and expected to vest	8 years 8 months 5 days
Weighted average remaining contractual term, Exercisable	6 years 2 months 5 days