Debt - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Total long-term debt, including current maturities	$ 3,390.2	$ 4,190.6
Capital lease obligations	46.2
Capital lease obligations		45.8
Less current portion	(6.4)	(843.0)
Less unamortized debt premium and debt issuance fees	(38.8)	(40.7)
Total long-term debt	3,345.0	3,306.9
Secured Debt \| Senior Secured Term Loan A Facility Due 2022
Debt Instrument [Line Items]
Total long-term debt, including current maturities	0.0	319.4
Secured Debt \| Senior Secured Term Loan Facility due 2027
Debt Instrument [Line Items]
Total long-term debt, including current maturities	550.0	0.0
Secured Debt \| Senior Secured Term Loan B Facility due 2025
Debt Instrument [Line Items]
Total long-term debt, including current maturities	0.0	313.5
Senior Notes \| 6.375% Senior Notes due 2026
Debt Instrument [Line Items]
Total long-term debt, including current maturities	0.0	750.0
Senior Notes \| 4.625% Senior Notes due 2026
Debt Instrument [Line Items]
Total long-term debt, including current maturities	794.0	761.9
Senior Notes \| 7.750% Senior Notes due 2027
Debt Instrument [Line Items]
Total long-term debt, including current maturities	600.0	600.0
Senior Notes \| Senior Notes, 4.375%, Due 2029
Debt Instrument [Line Items]
Total long-term debt, including current maturities	800.0	800.0
Senior Notes \| Senior Notes, 4.750%, Due 2028
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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