Income Taxes - Reconciliation of Expected Statutory Federal Income Tax Provision to Actual Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected income tax benefit at federal statutory tax rate	$ (3,904)	$ (10,216)
State income taxes, net of federal benefit	(1,390)	(3,005)
Tax credits	(374)	(3,666)
Change in valuation allowance	603	12,706
Return to provision adjustments	(358)	441
Stock compensation	3,934	251
Reserve for uncertain tax positions	1,444	3,596
Other	46	(45)
Income tax expense	$ 1	$ 62