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Balance Sheet Information - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2017
Balance Sheet Related Disclosures [Abstract]      
Depreciation expense $ 76.2 $ 64.6 $ 60.7
Amortization of unfavorable lease liability 5.7 6.6 $ 6.8
Write off of unfavorable lease liability $ 0.8 $ 1.2