Income Taxes - Schedule of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Non-current deferred tax assets:
Net operating loss	$ 28,264	$ 26,710
Research and development credits	9,820	9,820
Other credits	4,164	4,164
Operating lease liabilities	2,045	1,843
Stock-based compensation	400	945
Property and equipment and intangible assets	429	238
Accruals and reserves	209	111
Other	0	2
Gross non-current deferred tax assets	45,331	43,833
Right-of-use assets, operating leases	(1,826)	(1,515)
Total non-current deferred tax liabilities	(1,826)	(1,515)
Total deferred tax assets	43,505	42,318
Valuation allowance	(43,368)	(42,216)
Net deferred tax assets	$ 137	$ 102