Financial Instruments (Schedule of Interest Rate Swaps and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
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 %	2.28%	2.28%
Years Average Maturity	1 year 4 months	2 years 4 months
Cross Currency Interest Rate Swaps | Designated as Hedging Instrument | Net Investment Hedges
Derivative [Line Items]
US$ Notional	$ 539.7	$ 517.7
Average Pay %	3.27%	3.24%
Average Receive %	2.59%	2.43%
Years Average Maturity	1 year 11 months	2 years 7 months
Cross Currency Interest Rate Swaps | Designated as Hedging Instrument | Cash Flow Hedges
Derivative [Line Items]
US$ Notional	$ 1,095.7	$ 1,088.9
Average Pay %	4.96%	4.77%
Average Receive %	2.78%	2.72%
Years Average Maturity	2 years 5 months	3 years 4 months
Cross Currency Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative [Line Items]
US$ Notional	$ 41.6	$ 27.4
Average Pay %	3.28%	3.62%
Average Receive %	2.32%	0.81%
Years Average Maturity	1 year 8 months	1 year 10 months