Convertible Preferred Stock and Stockholders' Equity - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Number of Outstanding Options
Balance at December 31, 2019 | shares	1,684,630
Granted | shares	1,812,016
Cancelled | shares	(109,835)
Exercised | shares	(54,266)
Balance at September 30, 2020 | shares	3,332,545	1,684,630
Vested and expected to vest at September 30, 2020 | shares	3,332,545
Weighted Average Exercise Price
Balance at December 31, 2019 | $ / shares	$ 2.47
Granted | $ / shares	7.20
Cancelled | $ / shares	5.14
Exercised | $ / shares	1.27
Balance at September 30, 2020 | $ / shares	4.98	$ 2.47
Vested and expected to vest at September 30, 2020 | $ / shares	$ 4.98
Weighted Average Remaining Contractual Term (In Years)
Balance	8 years 10 months 6 days	8 years 8 months 23 days
Vested and expected to vest at September 30, 2020	8 years 10 months 6 days
Aggregate Intrinsic Value
Balance | $	$ 17,525	$ 911
Vested and expected to vest at September 30, 2020 | $	$ 17,525