Financial Instruments (Interest Rate Management Contracts and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Interest rate swaps contracts | Designated as Hedging Instrument | Fair value hedges
Derivative [Line Items]
Notional Principal amount	$ 800.0	$ 800.0
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]	Secured Overnight Financing Rate (SOFR) [Member]	Secured Overnight Financing Rate (SOFR) [Member]
Average Receive %	1.64%	1.64%
Years Average Maturity	2 years	3 years
Interest rate swaps contracts | Designated as Hedging Instrument | Cash flow hedges
Derivative [Line Items]
Notional Principal amount	$ 3,106.0	$ 2,159.3
Average Pay %	2.78%	2.72%
Years Average Maturity	20 years 1 month 6 days	21 years 2 months 12 days
Derivative Description of Variable Rate Basis-Receive	SOFR	SOFR
Interest rate swaps contracts | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Principal amount	$ 269.1	$ 461.4
Average Pay %	3.28%	3.27%
Years Average Maturity	20 years 2 months 12 days	20 years 6 months
Derivative Description of Variable Rate Basis-Receive	SOFR	SOFR
Cross currency interest rate swaps | Designated as Hedging Instrument | Net investment hedges
Derivative [Line Items]
Notional Principal amount	$ 70.3	$ 16.7
Average Pay %	4.86%	5.39%
Average Receive %	4.53%	3.64%
Years Average Maturity	6 months	2 months 12 days
Cross currency interest rate swaps | Designated as Hedging Instrument | Cash flow hedges
Derivative [Line Items]
Notional Principal amount	$ 247.7	$ 410.6
Average Pay %	5.21%	4.96%
Average Receive %	3.12%	2.80%
Years Average Maturity	1 year 7 months 6 days	1 year 10 months 24 days
Cross currency interest rate swaps | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Principal amount	$ 0.0	$ 34.7
Average Pay %	0.00%	5.39%
Average Receive %	0.00%	3.64%
Years Average Maturity	0 years	2 months 12 days