Financial Instruments (Schedule of Interest Rate Swaps and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2019	Sep. 30, 2018
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%	2.60%
Years Average Maturity	10 months 24 days	1 year 7 months 6 days
Cross Currency Interest Rate Swaps | Designated as Hedging Instrument | Net Investment Hedges
Derivative [Line Items]
US$ Notional	$ 246.6	$ 201.7
Average Pay %	4.55%	4.42%
Average Receive %	3.09%	2.97%
Years Average Maturity	2 years 10 months 24 days	3 years 1 month 6 days
Cross Currency Interest Rate Swaps | Designated as Hedging Instrument | Cash Flow Hedges
Derivative [Line Items]
US$ Notional	$ 1,063.5	$ 1,052.7
Average Pay %	4.85%	4.99%
Average Receive %	2.94%	2.89%
Years Average Maturity	2 years 2 months 12 days	2 years 3 months 18 days
Cross Currency Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative [Line Items]
US$ Notional	$ 29.6	$ 80.2
Average Pay %	4.17%	4.88%
Average Receive %	3.61%	3.43%
Years Average Maturity	4 years 7 months 6 days	3 years 10 months 24 days