Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Details)

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Income Taxes - Additional Information (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Line Items]      
Provision for income taxes $ 0 $ 0 $ 0
Net increase in valuation allowance $ 12,600,000 11,600,000  
Limitations in use of net operating losses Events which cause limitations in the amount of net operating losses that the Company may utilize in any one year include, but are not limited to, a cumulative ownership change of more than 50%, as defined, over a three-year testing period.    
Period for cumulative ownership change 3 years    
Unrecognized tax benefits if recognized that would impact effective tax rate $ 3,800,000 $ 2,800,000 $ 2,300,000
Interest and penalties incurred $ 0    
Corporate tax rate 21.00% 21.00% 34.00%
Reduction in deferred tax assets and valuation allowance $ 12,300,000    
Minimum      
Income Tax Disclosure [Line Items]      
Cumulative change in ownership percentage 50.00%    
Maximum      
Income Tax Disclosure [Line Items]      
Corporate tax rate     35.00%
Federal      
Income Tax Disclosure [Line Items]      
Net operating loss carryforwards $ 120,700,000    
Operating loss carryforwards expiration year 2032    
Federal | Research and Development Expenses      
Income Tax Disclosure [Line Items]      
General business credits $ 14,800,000    
Tax credit carryforward expiration year 2023    
State      
Income Tax Disclosure [Line Items]      
Net operating loss carryforwards $ 75,100,000    
Operating loss carryforwards expiration year 2030    
State | Research and Development Expenses      
Income Tax Disclosure [Line Items]      
General business credits $ 11,500,000