Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Financing costs, net	$ (11.9)	$ (13.9)
Total debt, net	1,132.2	1,139.8
Less: Current portion of long-term debt	10.4	12.3
Total long-term debt, net	1,121.8	1,127.5
Insurance Policy
Debt Instrument [Line Items]
Debt instruments net of original issue discount		1.9
Series B Term Loan
Debt Instrument [Line Items]
Debt instruments net of original issue discount	1,004.2	1,011.8
Receivables Financing Agreement
Debt Instrument [Line Items]
Debt instruments net of original issue discount	$ 139.9	$ 140.0

Debt instrument carrying amount net of issue discount.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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