Stock-Based Compensation - Stock Option Activity (Details) - $ / shares	9 Months Ended
	Sep. 30, 2019
Number of shares
Balance at beginning of period	489,222
Granted	86,485
Exercised	(1,892)
Early exercised	(471)
Canceled/forfeited	(21,614)
Balance at end of period	551,730
Vested and expected to vest at end of period	551,730
Exercisable at end of period	461,414
Weighted average exercise price per share
Balance at beginning of period (in dollars per share)	$ 5.84
Granted ( in dollars per share)	7.54
Exercised (in dollars per share)	5.93
Early exercised (in dollars per share)	5.93
Canceled/forfeited (in dollars per share)	6.98
Balance at end of period (in dollars per share)	6.07
Vested and expected to vest at end of period (in dollars per share)	6.07
Exercisable at end of period (in dollars per share)	$ 5.47
Weighted average remaining contractual term
Weighted average remaining contractual term, outstanding	7 years 3 months 15 days
Weighted average remaining contractual term, Vested and expected to vest	7 years 3 months 15 days
Weighted average remaining contractual term, Exercisable	5 years 7 months 17 days