Stock Plans and Stock Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Number of Shares
Beginning balance (in shares)	10,363,769
Granted (in shares)	4,313,500
Exercised (in shares)	0
Canceled/Forfeited (in shares)	(333,563)
Ending balance (in shares)	14,343,706	10,363,769
Exercisable at end of period (in shares)	6,884,853
Vested and unvested expected to vest at end of period (in shares)	13,445,514
Weighted Average Exercise Price per Share
Beginning balance (in dollars per share)	$ 3.80
Granted (in dollars per share)	3.21
Exercised (in dollars per share)	0
Canceled/Forfeited (in dollars per share)	8.39
Ending balance (in dollars per share)	3.51	$ 3.80
Exercisable at end of period (in dollars per share)	3.31
Vested and unvested expected to vest at end of period (in dollars per share)	$ 3.49
Weighted Average Remaining Contractual Life
Outstanding at end of period	7 years 11 months 12 days	7 years 4 months 28 days
Exercisable at end of period	6 years 9 months 3 days
Vested and unvested expected to vest at end of period	7 years 10 months 6 days
Aggregate Intrinsic Value
Outstanding at end of period	$ 7,333
Exercisable at end of period	5,247
Vested and unvested expected to vest at end of period	$ 7,193