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Revenue Recognition - Additional Information (Detail) - USD ($)
$ in Millions
6 Months Ended
Mar. 31, 2020
Sep. 30, 2019
Revenue From Contract With Customer [Abstract]    
Contract assets recorded in prepaid expenses and other current assets $ 3.6 $ 2.5
Revenue remaining obligation description As a practical expedient, since repair and maintenance service contracts have an original duration of one year or less, we do not consider the time value of money, and we do not disclose estimated revenue expected to be recognized in the future for performance obligations that are unsatisfied (or partially unsatisfied) at the end of the reporting period or when we expect to recognize such revenue.