Stock Based Compensation - Stock option activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Sep. 30, 2020 USD ($) $ / shares
Aggregate Intrinsic Value
Proceeds from exercise of stock options | $	$ 347	$ 84
Stock options
Number of Shares
Outstanding at beginning of period (in shares) | shares	1,625,256
Granted (in shares) | shares	1,166,904
Exercised (in shares) | shares	(401,322)
Forfeited (in shares) | shares	(21,275)
Outstanding at end period (in shares) | shares	2,369,563
Vested and exercisable (in shares) | shares	391,322
Unvested and exercisable (in shares) | shares	1,978,241
Weighted Average Exercise Price
Weighted-Average Exercise Price Outstanding at beginning period (in dollars per share)	$ 1.88
Weighted Average Exercise Price Granted (in dollars per share)	9.36
Weighted Average Exercise Price Exercised (in dollars per share)	2.18
Weighted Average Exercise Price Forfeited (in dollars per share)	3.07
Weighted Average Exercise Price Outstanding at end period (in dollars per share)	5.51
Weighted Average Exercise Price Vested and exercisable (in dollars per share)	1.84
Weighted Average Exercise Price Unvested and exercisable (in dollars per share)	$ 6.24
Weighted Average Contractual Term (in years)
Weighted Average Contractual Term, Outstanding (in years)	8 years 11 months 26 days
Weighted Average Contractual Term, Vested and exercisable (in years)	7 years 8 months 4 days
Weighted Average Contractual Term, Unvested and exercisable (in years)	9 years 3 months
Aggregate Intrinsic Value
Aggregate Intrinsic Value Outstanding | $	$ 20,029
Aggregate Intrinsic Value Vested and exercisable | $	4,746
Aggregate Intrinsic Value Unvested and exercisable | $	15,283
Aggregate intrinsic value of stock options exercised | $	2,300
Proceeds from exercise of stock options | $	$ 900
Weighted-average grant-date fair value of stock options granted	$ 6.02	$ 1.38
Unrecognized compensation cost | $	$ 7,700
Unrecognized compensation cost, weighted-average period for recognition	3 years 3 months 18 days