Income Taxes - Reconciliation Between Income Taxes at Statutory Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Taxes
Loss before income taxes	$ (10,440)	$ (10,882)
Tax (benefit) at statutory tax rate	(2,193)	(2,285)
Effects of:
Exclusion of incentive stock option expense	73	50
R&D tax credits	(451)	(832)
Increase (decrease) in valuation allowance	2,648	2,990
Other	(77)	77
Provision for income taxes	0	0
Unrecognized tax benefits	0
Unrecognized tax benefits, interest and penalties recorded	0
Unrecognized tax benefits, interest and penalties accrued	$ 0	$ 0