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Income Taxes - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Line Items]        
Provisional tax benefit due to new Tax Act       $ 122,000
Untaxed accumulated unremitted foreign earnings       813,000
Valuation allowance, deferred tax assets $ 37,856,000 $ 30,363,000    
Research and development tax credit carryforwards 29,046,000 27,607,000    
Accrued interest 2,297,000 2,070,000 $ 1,462,000 $ 1,104,000
Net interest expense 17,000 7,000 $ 7,000  
Potential payment of interest 58,000 41,000    
Stock-based compensation 1,796,000 $ 1,587,000    
Maximum [Member]        
Income Tax Disclosure [Line Items]        
Stock-based compensation 49,500,000      
Domestic Tax Authority [Member]        
Income Tax Disclosure [Line Items]        
Federal net operating loss carryforwards expiry, beginning year       2025
Research and development tax credit carryforwards       $ 11,344,000
Domestic Tax Authority [Member] | Tax Year 2017 [Member]        
Income Tax Disclosure [Line Items]        
Net operating loss carryforwards $ 24,990,000      
Certain States [Member]        
Income Tax Disclosure [Line Items]        
Federal net operating loss carryforwards expiry, beginning year       2020
Research and development tax credit carryforwards       $ 19,423,000
VICR Certain States Member [Member] | Tax Year 2017 [Member]        
Income Tax Disclosure [Line Items]        
Federal net operating loss carryforwards expiry, beginning year 2024      
Net operating loss carryforwards $ 10,241,000