Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation between the amount of reported income tax and the amount computed using U.S. Statutory rate
Pre-tax loss	$ (70,738)	$ (60,947)	$ (50,878)
Loss at statutory rates	(14,855)	(12,799)	(10,684)
Research and development credits	(2,422)	(1,778)	(1,902)
State taxes	(7,082)	(5,802)	(2,170)
Other	(941)	(1,152)	(1,011)
Change in fair value remeasurement of contingent consideration	(295)	(886)	(272)
Expiration of NOLs and R&D credit	14,210	20,294	18,966
Change in valuation allowance	11,158	956	$ (2,927)
Income tax (benefit) provision	$ (227)	$ (1,167)