Income Taxes - Income Tax (Provision) for Federal Statutory Corporate Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Taxes
Tax benefit at federal statutory rate	$ 1,674	$ 1,244
State income tax benefit (provision), net of federal benefit	335	244
Research and development tax credits	361	272
Foreign earnings or losses taxed at different rates	(28)	(38)
Tax rate change, due primarily to loss carryback	(2)	2,720
Other	(31)	(615)
Change in valuation allowance	(2,026)	2,602
Tax provision	$ 283	$ 6,429