Financial Instruments (Schedule of Outstanding Currency Price Risk Management Instruments) (Details) - Forward Exchange Contracts - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
US$ Notional	$ 4,385.8	$ 4,099.5
Years Average Maturity	10 months	10 months
Designated as Hedging Instrument | Cash Flow Hedges
Derivative [Line Items]
US$ Notional	$ 2,905.0	$ 3,150.2
Years Average Maturity	5 months	5 months
Designated as Hedging Instrument | Net Investment Hedges
Derivative [Line Items]
US$ Notional	$ 359.8	$ 675.5
Years Average Maturity	2 years 2 months	3 years
Not Designated as Hedging Instrument
Derivative [Line Items]
US$ Notional	$ 1,121.0	$ 273.8
Years Average Maturity	1 year 5 months	1 month