Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryovers	$ 87,877	$ 82,747
Research and development and other tax credits	35,344	34,337
Intangibles and property and equipment basis difference	607	715
Stock compensation expense	587	283
Lease liability	631	88
Other	564	281
Total deferred tax assets	125,610	118,451
Total deferred tax liabilities	(782)	(282)
Net deferred tax asset	124,828	118,169
Valuation allowance	(124,828)	(118,169)
Net deferred tax asset	$ 0	$ 0