Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 88,279	$ 87,216
Research credit carryforward	7,026	7,071
Capitalized research and development expenses	164	205
Stock options and other	5,028	2,092
Total gross deferred tax assets	100,497	96,584
Valuation allowance for deferred tax assets	(100,497)	(96,584)
Net deferred tax assets	0	0
Valuation allowance
Increase (decrease) in the valuation allowance	$ 3,900	$ 5,400