Financial Instruments (Interest Rate Management Contracts and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2023	Sep. 30, 2022
Interest Rate Swaps Contracts | Designated as hedging instrument | Fair Value Hedges
Derivative [Line Items]
US$ Notional	$ 800.0	$ 800.0
Average Pay %	Various	Various
Average Receive %	1.64%	1.64%
Years Average Maturity	4 years 2 months 12 days	5 years
Interest Rate Swaps Contracts | Designated as hedging instrument | Cash flow hedges
Derivative [Line Items]
US$ Notional	$ 1,006.7	$ 0.0
Average Pay %	2.82%	0.00%
Average Receive %	SOFR	—
Years Average Maturity	22 years 3 months 18 days	0 years
Cross currency interest rate swaps | Designated as hedging instrument | Net investment hedges
Derivative [Line Items]
US$ Notional	$ 152.8	$ 176.7
Average Pay %	3.92%	4.12%
Average Receive %	3.02%	3.07%
Years Average Maturity	9 months 18 days	1 year 2 months 12 days
Cross currency interest rate swaps | Designated as hedging instrument | Cash flow hedges
Derivative [Line Items]
US$ Notional	$ 630.3	$ 785.7
Average Pay %	4.75%	4.78%
Average Receive %	3.05%	3.05%
Years Average Maturity	2 years 1 month 6 days	2 years 3 months 18 days
Cross currency interest rate swaps | Not designated as hedging instrument
Derivative [Line Items]
US$ Notional	$ 17.6	$ 37.7
Average Pay %	5.39%	5.39%
Average Receive %	3.54%	3.54%
Years Average Maturity	6 months	1 year 2 months 12 days