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Commitments and Contingencies - Additional Information (Detail) - USD ($)
12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]      
Costs incurred for store closings and lease terminations $ 1,700,000 $ 3,100,000 $ 0
Workers compensation insurance policies $ 1,100,000