Stock Option Plans - Schedule of activity of stock option plan (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2022	Jun. 30, 2021	Dec. 31, 2021
Stock Number of Options
Beginning balance (in shares)	2,374,504
Options granted (in shares)	0
Options exercised (in shares)	0
Options cancelled or expired and returned to plan (in shares)	(717,331)
Ending balance (in shares)	1,657,173
Vested and exercisable to vest (in shares)	723,575
Vested and expected (in shares)	1,440,785
Weighted- Average Exercise Price
Beginning balance (in dollars per share)	$ 3.00
Options granted (in dollars per share)	0
Options exercised (in dollars per share)	0
Options cancelled or expired and returned to plan (in dollars per share)	3.00
Ending balance (in dollars per share)	3.01
Vested and exercisable to vest (in dollars per share)	2.98
Vested and expected (in dollars per share)	$ 3.00
Weighted- Average Remaining Contractual Term (Years)
Outstanding	7 years 11 months 8 days	8 years 3 months
Vested and exercisable to vest	7 years 8 months 15 days
Vested and expected	7 years 10 months 24 days
Aggregate Intrinsic Value (in thousands)
Outstanding	$ 0		$ 375
Vested and exercisable to vest	0
Vested and expected	$ 0