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Income Taxes - Additional Information (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Line Items]        
Uncertain tax benefits $ 393,000 $ 271,000 $ 408,000 $ 119,000
Interest or penalties recognized for the period 0 $ 0    
Federal        
Income Tax Disclosure [Line Items]        
Net operating loss carryforwards 186,500,000      
Research credit carryforwards $ 800,000      
Tax credit carry forwards expiration year 2039      
Federal | Research        
Income Tax Disclosure [Line Items]        
Research credit carryforward $ 1,300,000      
State        
Income Tax Disclosure [Line Items]        
Net operating loss carryforwards $ 148,800,000      
Operating loss carry forwards expiration year 2034      
California        
Income Tax Disclosure [Line Items]        
Research credit carryforwards $ 900,000