Stock-Based Compensation - Stock Option Activity Under Stock Option Plan (Details) - $ / shares	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Number of Shares
Beginning Balance	10,665,869
Granted	2,690,000	4,314,438
Cancelled	(2,386,216)
Ending Balance	10,969,653		10,665,869
Options exercisable, at end of period	3,394,055		4,410,312
Options available for future grant	15,242,103
Weighted Average Exercise Price
Beginning Balance	$ 2.87
Granted	0.69
Cancelled	3.68
Ending Balance	2.16		$ 2.87
Options exercisable, at end of period	$ 3.35		$ 3.85
Weighted Average Contractual Term (Years)
Outstanding, at end of period	9 years 7 days
Options exercisable, at end of period	7 years 10 months 9 days		7 years 6 months 10 days