Fair Value , Assets and Liabilities Measured on Nonrecurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2023	Sep. 30, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	$ 1,491.9	$ 1,490.5
2026 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes, Noncurrent	497.3	496.8
2031 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes, Noncurrent	494.8	494.5
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Fair Value Disclosure	1,369.0	1,297.3
Fair Value, Inputs, Level 2 [Member] | 2026 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	452.9	431.2
Fair Value, Inputs, Level 2 [Member] | 2031 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	420.5	377.6
2023 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes, Current	499.8	499.2
2023 Notes | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-Term Debt, Fair Value	$ 495.6	$ 488.5