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Refundable Research and Development Credit and Income Taxes - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Income Tax Expense Benefit Continuing Operations [Abstract]        
Current income tax expense or benefits $ 0 $ 0 $ 0 $ 0
Deferred income tax expense or benefits $ 0 $ 0 $ 0 $ 0