Financial Instruments (Fair Value of Derivative Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Sep. 30, 2018
Derivative [Line Items]
Total Derivatives, Assets	$ 136.6	$ 146.1
Total Derivatives, Liabilities	95.9	94.1
Designated as Hedging Instrument
Derivative [Line Items]
Total Derivatives, Assets	105.0	117.7
Total Derivatives, Liabilities	56.4	55.5
Designated as Hedging Instrument | Other Receivables | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	32.8	24.9
Designated as Hedging Instrument | Other Receivables | Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Assets	16.1	24.3
Designated as Hedging Instrument | Other Noncurrent Assets | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	29.2	19.8
Designated as Hedging Instrument | Other Noncurrent Assets | Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Assets	26.9	48.7
Designated as Hedging Instrument | Accrued Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	39.6	37.0
Designated as Hedging Instrument | Accrued Liabilities | Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	0.9	2.3
Designated as Hedging Instrument | Other Noncurrent Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	1.1	4.6
Designated as Hedging Instrument | Other Noncurrent Liabilities | Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	14.8	11.6
Not Designated as Hedging Instrument
Derivative [Line Items]
Total Derivatives, Assets	31.6	28.4
Total Derivatives, Liabilities	39.5	38.6
Not Designated as Hedging Instrument | Other Receivables | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	8.2	7.9
Not Designated as Hedging Instrument | Other Receivables | Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Assets	0.0	4.0
Not Designated as Hedging Instrument | Other Noncurrent Assets | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	23.3	16.2
Not Designated as Hedging Instrument | Other Noncurrent Assets | Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Assets	0.1	0.3
Not Designated as Hedging Instrument | Accrued Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	13.2	14.9
Not Designated as Hedging Instrument | Accrued Liabilities | Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	0.0	0.0
Not Designated as Hedging Instrument | Other Noncurrent Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	26.3	23.7
Not Designated as Hedging Instrument | Other Noncurrent Liabilities | Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	$ 0.0	$ 0.0