Financial Instruments (Carrying Amount and Cumulative Hedging Adjustment) (Details) - USD ($) $ in Millions	Jun. 30, 2025	Sep. 30, 2024
Current portion of long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying amounts of hedged item	$ 547.9	$ 0.0
Cumulative hedging adjustment, included in carrying amount	(2.0)	0.0
Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying amounts of hedged item	1,518.9	2,057.1
Cumulative hedging adjustment, included in carrying amount	$ (26.3)	$ (36.6)