Equity Incentive Plans - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Subject to Options Outstanding, Outstanding as of December 31, 2019 | shares	8,538,060
Shares Subject to Options Outstanding, Options granted | shares	1,911,222
Shares Subject to Options Outstanding, Option exercised | shares	(44,007)
Shares Subject to Options Outstanding, Options forfeited/cancelled | shares	(541,572)
Shares Subject to Options Outstanding, Outstanding as of June 30,2020 | shares	9,863,703	8,538,060
Shares Subject to Options Outstanding, Options vested and exercisable as of June 30, 2020 | shares	2,791,102
Weighted-Average Exercise Price, Outstanding as of December 31, 2019 | $ / shares	$ 13.67
Weighted-Average Exercise Price, Options granted | $ / shares	14.30
Weighted-Average Exercise Price, Option exercised | $ / shares	3.49
Weighted-Average Exercise Price, Options forfeited/cancelled | $ / shares	12.96
Weighted-Average Exercise Price, Outstanding as of June 30, 2020 | $ / shares	13.88	$ 13.67
Weighted-Average Exercise Price, Options vested and exercisable as of June 30,2020 | $ / shares	$ 12.31
Weighted-Average Remaining Contractual Life (Years), Outstanding as of December 31, 2019	8 years 7 months 6 days	9 years
Weighted-Average Remaining Contractual Life (Years), Options vested and exercisable as of June 30, 2020	8 years
Aggregate Intrinsic Value, Outstanding as of 31 Dec, 2019 | $	$ 22,225	$ 35,385
Aggregate Intrinsic Value, Options vested and exercisable | $	$ 9,989