Debt - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Total long-term debt, including current maturities	$ 3,382.0	$ 3,515.3
Capital lease obligations	46.1
Capital lease obligations		46.9
Less current portion	(93.0)	(1.6)
Less unamortized debt premium and debt issuance fees	(36.5)	(52.1)
Total long-term debt	3,252.5	3,461.6
Secured Debt \| 2019 Senior Secured Term Loan A Facility Due 2022
Debt Instrument [Line Items]
Total long-term debt, including current maturities	342.2	0.0
Secured Debt \| Senior Secured Term Loan A Facility due 2021
Debt Instrument [Line Items]
Total long-term debt, including current maturities	0.0	77.5
Secured Debt \| Senior Secured Term Loan B Facility due 2025
Debt Instrument [Line Items]
Total long-term debt, including current maturities	313.5	982.5
Senior Notes \| 5.50% Senior Notes due 2025
Debt Instrument [Line Items]
Total long-term debt, including current maturities	600.0	600.0
Senior Notes \| 6.375% Senior Notes due 2026
Debt Instrument [Line Items]
Total long-term debt, including current maturities	750.0	500.0
Senior Notes \| 4.625% Senior Notes due 2026
Debt Instrument [Line Items]
Total long-term debt, including current maturities	730.2	708.4
Senior Notes \| 7.750% Senior Notes due 2027
Debt Instrument [Line Items]
Total long-term debt, including current maturities	$ 600.0	$ 600.0

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Present value of lessee's discounted obligation for lease payments from finance lease.

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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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