Financial Instruments (Interest Rate Management Contracts and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Interest rate swaps contracts | Designated as Hedging Instrument | Fair value hedges
Derivative [Line Items]
Notional Principal amount	$ 800.0	$ 800.0
Average Pay %	SOFR	SOFR
Average Receive %	1.64%	1.64%
Years Average Maturity	3 years	4 years
Interest rate swaps contracts | Designated as Hedging Instrument | Cash flow hedges
Derivative [Line Items]
Notional Principal amount	$ 2,159.3	$ 1,182.5
Average Pay %	2.72%	2.82%
Years Average Maturity	21 years 2 months 12 days	22 years 1 month 6 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	$ 461.4	$ 0.0
Average Pay %	3.27%	0.00%
Years Average Maturity	20 years 6 months	0 years
Derivative Description of Variable Rate Basis-Receive	SOFR	—
Cross currency interest rate swaps | Designated as Hedging Instrument | Net investment hedges
Derivative [Line Items]
Notional Principal amount	$ 16.7	$ 80.8
Average Pay %	5.39%	4.60%
Average Receive %	3.64%	3.65%
Years Average Maturity	2 months 12 days	10 months 24 days
Cross currency interest rate swaps | Designated as Hedging Instrument | Cash flow hedges
Derivative [Line Items]
Notional Principal amount	$ 410.6	$ 598.2
Average Pay %	4.96%	4.89%
Average Receive %	2.80%	3.22%
Years Average Maturity	1 year 10 months 24 days	2 years 2 months 12 days
Cross currency interest rate swaps | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Principal amount	$ 34.7	$ 44.5
Average Pay %	5.39%	5.39%
Average Receive %	3.64%	3.54%
Years Average Maturity	2 months 12 days	2 months 12 days