Commitment and Contingencies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020		Sep. 30, 2019	[1]
Commitments And Contingencies [Line Items]
Reserve for unpaid and incurred but not reported claims, amount	$ 154.7	$ 151.1
Reserve for unpaid and incurred but not reported claims, classified in current liabilities	50.2	48.4
Reserve for unpaid and incurred but not reported claims, classified in non-current liabilities	104.5	102.7
Claims recoverable from third party insurance carriers	30.5	34.1
Charge related to changes in self-insured liability estimates	24.1	24.1	[1]	$ 0.0
Other Current Assets
Commitments And Contingencies [Line Items]
Claims recoverable from third party insurance carriers	8.2	8.1
Other Assets
Commitments And Contingencies [Line Items]
Claims recoverable from third party insurance carriers	$ 22.3	$ 26.0

[1] Represents expenses related to changes in estimates and actuarial assumptions associated with the Company’s self-insured liability amounts for workers’ compensation, general liability, auto liability, and employee health care insurance programs, to reflect uncertainties associated with the current environment, including the COVID-19 pandemic.