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Income Taxes - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Taxes [Line Items]      
Increase (decrease) in deferred tax assets valuation allowance $ (26,600,000) $ (29,600,000) $ (45,300,000)
Deferred tax assets, net operating loss carryforwards for federal 622,600,000    
Deferred tax assets, net operating loss carryforwards for state 261,700,000    
Federal research tax credit carryforwards 21,900,000    
State research tax credit carryforwards 18,300,000    
Accrued interest and/or penalties 0    
French      
Income Taxes [Line Items]      
Deferred tax assets, net operating loss carryforwards for foreign $ 145,900,000