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Stock Option and Incentive Plan - Summary of Option Activity (Parenthetical) (Detail)
12 Months Ended
Sep. 30, 2020
Disclosure of Stock Option and Incentive Plan [Abstract]  
Weighted average remaining contractual life of outstanding options 7 years 1 month 28 days
Weighted average remaining contractual life of exercisable options 5 years 8 months 4 days