Financial Instruments (Schedule of Interest Rate Management Contracts and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Interest Rate Swaps Contracts | Designated as Hedging Instrument | Fair Value Hedges
Derivative [Line Items]
US$ Notional	$ 600.0	$ 600.0
Average Pay %	LIBOR	LIBOR
Average Receive %	2.60%	2.28%
Years Average Maturity	1 year 7 months 6 days	1 year 3 months 18 days
Cross Currency Interest Rate Swaps | Designated as Hedging Instrument | Net Investment Hedges
Derivative [Line Items]
US$ Notional	$ 201.7	$ 539.7
Average Pay %	4.42%	3.27%
Average Receive %	2.97%	2.59%
Years Average Maturity	3 years 1 month 6 days	1 year 10 months 24 days
Cross Currency Interest Rate Swaps | Designated as Hedging Instrument | Cash Flow Hedges
Derivative [Line Items]
US$ Notional	$ 1,052.7	$ 1,095.7
Average Pay %	4.99%	4.96%
Average Receive %	2.89%	2.78%
Years Average Maturity	2 years 3 months 18 days	2 years 4 months 24 days
Cross Currency Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative [Line Items]
US$ Notional	$ 80.2	$ 41.6
Average Pay %	4.88%	3.28%
Average Receive %	3.43%	2.32%
Years Average Maturity	3 years 10 months 24 days	1 year 8 months 12 days