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Income Taxes - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Line Items]      
Income tax benefits for the net operating losses $ 0 $ 0  
Valuation allowance $ 53,834,000 40,290,000 $ 26,515,000
Description of tax benefit likely to be realized upon settlement greater than 50%    
Unrecognized tax benefits $ 0    
Income tax examination description In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations. Tax years from 2016 to the present are open to examination under the statute.    
Interest or penalties accrued $ 0 0  
Federal      
Income Tax Disclosure [Line Items]      
Net operating loss carryforwards 172,900,000 125,500,000  
Net operating loss carryforwards subject to expiration 79,400,000    
Net operating loss carryforwards not subject to expiration $ 93,500,000    
Net operating loss carryforwards expiration year 2034    
Federal | Research and Development.      
Income Tax Disclosure [Line Items]      
Tax credit carryforwards $ 2,500,000    
State      
Income Tax Disclosure [Line Items]      
Net operating loss carryforwards $ 159,000,000 $ 109,400,000  
Net operating loss carryforwards expiration year 2029    
State | Research and Development.      
Income Tax Disclosure [Line Items]      
Tax credit carryforwards $ 1,800,000