Income Taxes - Reconciliation of Effective Tax Rate to the Statutory Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Amount
Income tax (benefit) expense at federal statutory rate	$ (5,606)	$ 1,818
State income tax, net of federal benefit	(1,979)	618
Non-deductible warrant expense	0	284
Other permanent differences	(185)	46
Research and development tax credits	(551)	(715)
Other tax credits	(555)	1
Tax reserve reassessment	(7)	25
Impact of CARES Act	(1,390)	0
Change in valuation allowance	6,348	(2,696)
Return adjustment	213	752
Stock-based compensation	104	279
Other, net	(105)	(3)
Total tax (benefit) expense	$ (3,713)	$ 409
Percent
Income tax (benefit) expense at federal statutory rate	21.00%	21.00%
State income tax, net of federal benefit	7.40%	7.10%
Non-deductible warrant expense	0.00%	3.30%
Other permanent differences	0.70%	0.50%
Research and development tax credits	2.10%	(8.30%)
Other tax credits	2.10%	0.00%
Tax reserve reassessment	0.00%	0.30%
Impact of CARES Act	5.20%	0.00%
Change in valuation allowance	(23.80%)	(31.10%)
Return adjustment	(0.80%)	8.70%
Stock-based compensation	(0.40%)	3.20%
Other, net	0.40%	0.00%
Income tax (benefit) expense	13.90%	4.70%