Financial Instruments (Carrying Amount and Cumulative Hedging Adjustment) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Sep. 30, 2025
Current portion of long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying amounts of hedged item	$ 0.0	$ 549.7
Cumulative hedging adjustment, included in carrying amount	0.0	(0.3)
Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying amounts of hedged item	1,524.7	1,522.5
Cumulative hedging adjustment, included in carrying amount	$ (21.5)	$ (23.1)