Financial Instruments (Schedule of Outstanding Currency Price Risk Management Instruments) (Details) - Forward Exchange Contracts - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Mar. 31, 2019	Sep. 30, 2018
Derivative [Line Items]
US$ Notional	$ 4,072.9	$ 4,682.7
Years Average Maturity	7 months 6 days	8 months 12 days
Designated as Hedging Instrument | Cash Flow Hedges
Derivative [Line Items]
US$ Notional	$ 2,773.8	$ 2,489.1
Years Average Maturity	4 months 24 days	4 months 24 days
Designated as Hedging Instrument | Net Investment Hedges
Derivative [Line Items]
US$ Notional	$ 472.4	$ 457.5
Years Average Maturity	1 year 2 months 12 days	1 year 8 months 12 days
Not Designated as Hedging Instrument
Derivative [Line Items]
US$ Notional	$ 826.7	$ 1,736.1
Years Average Maturity	1 year 1 month 6 days	9 months 18 days