Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Federal and state loss carryforwards	$ 3,031	$ 1,697
Reserves, accruals and other	239	156
Depreciation and amortization	1,284	1,629
Deferred stock-based compensation	2,698	2,613
Research and development credit carryforwards	6,613	6,707
Foreign tax and other credits		61
Total deferred tax assets	13,865	12,863
Less: Valuation allowance	$ (13,865)	(12,802)
Net deferred tax assets		$ 61