Long-term and Short-term Debt - Schedule of Carrying Amounts and Estimated Fair Values (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Carrying Value
Current portion of long-term debt	$ 2.0	$ 307.0
Long-term debt	2,614.0	2,561.0
Carrying Value
Carrying Value
Current portion of long-term debt	2.0	307.0
Long-term debt	2,614.0	2,561.0
Fair Value
Fair Value
Current portion of long-term debt	2.0	305.0
Long-term debt	$ 2,350.0	$ 2,334.0

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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+ Details