Financial Instruments (Fair Value of Derivative Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Derivative [Line Items]
Total Derivatives, Assets	$ 175.3	$ 227.8
Total Derivatives, Liabilities	127.9	131.9
Designated as Hedging Instrument
Derivative [Line Items]
Total Derivatives, Assets	168.3	222.5
Total Derivatives, Liabilities	119.2	128.7
Designated as Hedging Instrument | Other Receivables | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	58.6	81.7
Designated as Hedging Instrument | Other Receivables | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Assets	7.0	11.1
Designated as Hedging Instrument | Other Noncurrent Assets | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	23.2	27.1
Designated as Hedging Instrument | Other Noncurrent Assets | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Assets	79.5	102.6
Designated as Hedging Instrument | Accrued Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	44.3	82.0
Designated as Hedging Instrument | Accrued Liabilities | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Liabilities	14.8	10.7
Designated as Hedging Instrument | Other Noncurrent Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	21.9	13.8
Designated as Hedging Instrument | Other Noncurrent Liabilities | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Liabilities	38.2	22.2
Not Designated as Hedging Instrument
Derivative [Line Items]
Total Derivatives, Assets	7.0	5.3
Total Derivatives, Liabilities	8.7	3.2
Not Designated as Hedging Instrument | Other Receivables | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	2.4	1.1
Not Designated as Hedging Instrument | Other Receivables | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Assets	0.0	0.0
Not Designated as Hedging Instrument | Other Noncurrent Assets | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Assets	4.6	4.2
Not Designated as Hedging Instrument | Accrued Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	6.0	2.2
Not Designated as Hedging Instrument | Accrued Liabilities | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Liabilities	2.7	1.0
Not Designated as Hedging Instrument | Other Noncurrent Liabilities | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Liabilities	$ 0.0	$ 0.0