Stock Option Activity Under Stock Option Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Number of Shares
Beginning Balance			6,840,719
Granted	2,755,000	203,178	7,150,438	1,252,178
Exercised			(363,109)
Cancelled			(2,555,154)
Ending Balance	11,072,894		11,072,894		6,840,719
Options exercisable, at end of period	5,743,820		5,743,820		3,596,315
Options available for future grant	2,224,159		2,224,159
Weighted Average Exercise Price
Beginning Balance			$ 3.81
Granted			2.97
Exercised			2.86
Cancelled			3.54
Ending Balance	$ 3.36		3.36		$ 3.81
Options exercisable, at end of period	$ 4.08		$ 4.08		$ 4.17
Weighted Average Contractual Term (Years)
Outstanding, at end of period			8 years 3 months 25 days
Options exercisable, at end of period			7 years 2 months 26 days		6 years 10 months 24 days
Aggregate Intrinsic Value
Outstanding, at end of period	$ 473		$ 473
Options exercisable, at end of period	$ 0		$ 0		$ 598