Financial Instruments (Interest Rate Management Contracts and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Mar. 31, 2022	Sep. 30, 2021
Interest Rate Swaps Contracts | Designated as Hedging Instrument | Fair Value Hedges
Derivative [Line Items]
US$ Notional	$ 800.0	$ 200.0
Average Pay %	Various	LIBOR
Average Receive %	1.64%	2.76%
Years Average Maturity	5 years 6 months	1 month 6 days
Cross currency interest rate swaps | Designated as Hedging Instrument | Net Investment Hedges
Derivative [Line Items]
US$ Notional	$ 214.4	$ 210.2
Average Pay %	4.34%	4.32%
Average Receive %	3.15%	3.14%
Years Average Maturity	1 year 8 months 12 days	2 years 2 months 12 days
Cross currency interest rate swaps | Designated as Hedging Instrument | Cash Flow Hedges
Derivative [Line Items]
US$ Notional	$ 1,013.6	$ 1,005.7
Average Pay %	4.90%	4.98%
Average Receive %	2.92%	2.93%
Years Average Maturity	2 years 3 months 18 days	2 years 8 months 12 days
Cross currency interest rate swaps | Not Designated as Hedging Instrument
Derivative [Line Items]
US$ Notional	$ 0.0	$ 4.2
Average Pay %	0.00%	5.39%
Average Receive %	0.00%	3.54%
Years Average Maturity	0 years	2 years 2 months 12 days