Financial Instruments (Interest Rate Management Contracts and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Interest Rate Swaps Contracts | Designated as Hedging Instrument | Fair Value Hedges
Derivative [Line Items]
US$ Notional	$ 200.0	$ 200.0
Average Pay %	LIBOR	LIBOR
Average Receive %	2.76%	2.76%
Years Average Maturity	1 year 1 month 6 days	2 years 1 month 6 days
Cross Currency Interest Rate Swaps | Designated as Hedging Instrument | Net Investment Hedges
Derivative [Line Items]
US$ Notional	$ 201.6	$ 216.8
Average Pay %	4.27%	4.80%
Average Receive %	3.12%	3.31%
Years Average Maturity	3 years 2 months 12 days	3 years 6 months
Cross Currency Interest Rate Swaps | Designated as Hedging Instrument | Cash Flow Hedges
Derivative [Line Items]
US$ Notional	$ 1,057.9	$ 1,129.3
Average Pay %	4.83%	4.92%
Average Receive %	2.98%	3.04%
Years Average Maturity	2 years 6 months	2 years 3 months 18 days
Cross Currency Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative [Line Items]
US$ Notional	$ 12.8	$ 6.1
Average Pay %	5.39%	2.55%
Average Receive %	3.54%	3.72%
Years Average Maturity	3 years 2 months 12 days	4 years 6 months