Income Taxes - Deferred tax assets net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 56,030	$ 52,539	$ 42,344
Tax credit carryforwards	9,888	9,181	7,894
Capitalized tax assets	155	125	63
Accruals	124	137	207
Stock compensation	5,487	5,006	4,942
Operating lease liability	728	1,021	646
IRC 174 capitalization	4,518
Other	21	12	47
Total deferred tax assets	76,951	68,021	56,143
Deferred tax liabilities
Operating lease right-of-use asset	(620)	(893)	(461)
Valuation allowance	(76,331)	(67,128)	(55,682)
Net deferred tax assets	0	0	$ 0
Increase in valuation allowance	$ 9,200	$ 11,400