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Research and Development Costs - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Research And Development [Abstract]        
Research and Development Expense $ 4.5 $ 8.1 $ 17.4 $ 18.6