Stock Option Plans - Schedule of activity of stock option plan (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Stock Number of Options
Ending balance (in shares)	2,852,530	5,931,024
Beginning balance (in shares)	5,931,024
Options granted (in shares)	4,231
Options exercised (in shares)	(1,095,567)
Options cancelled or expired and returned to plan (in shares)	(1,987,158)
Vested and exercisable to vest (in shares)	643,414
Vested and expected (in shares)	1,986,567
Weighted- Average Exercise Price
Ending balance (in dollars per share)	$ 3.00	$ 2.61
Options granted (in dollars per share)	14.45
Options exercised (in dollars per share)	2.21
Options cancelled or expired and returned to plan (in dollars per share)	2.24
Vested and exercisable to vest (in dollars per share)	2.96
Vested and expected (in dollars per share)	$ 2.99
Weighted- Average Remaining Contractual Term (Years)
Outstanding	8 years 5 months 23 days	8 years 1 month 6 days
Vested and exercisable to vest	8 years 2 months 19 days
Vested and expected	8 years 4 months 9 days
Aggregate Intrinsic Value (in thousands)
Outstanding	$ 1,611	$ 70,192
Vested and exercisable to vest	400
Vested and expected	$ 1,146