Financial Instruments (Fair Value of Derivative Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Derivative [Line Items]
Total derivatives, asset	$ 325.5	$ 373.7
Total derivatives, liabilities	114.7	95.3
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total derivatives, asset	301.5	296.6
Total derivatives, liabilities	100.8	65.1
Hedges Not Designated [Member]
Derivative [Line Items]
Total derivatives, asset	24.0	77.1
Total derivatives, liabilities	13.9	30.2
Forward Exchange Contracts [Member] | Designated as Hedging Instrument [Member] | Other Receivables [Member]
Derivative [Line Items]
Total derivatives, asset	36.3	72.3
Forward Exchange Contracts [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Total derivatives, asset	72.6	44.4
Forward Exchange Contracts [Member] | Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Derivative [Line Items]
Total derivatives, liabilities	76.7	44.0
Forward Exchange Contracts [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Total derivatives, liabilities	1.2	9.1
Forward Exchange Contracts [Member] | Hedges Not Designated [Member] | Other Receivables [Member]
Derivative [Line Items]
Total derivatives, asset	20.3	77.1
Forward Exchange Contracts [Member] | Hedges Not Designated [Member] | Accrued Liabilities [Member]
Derivative [Line Items]
Total derivatives, liabilities	13.1	29.5
Interest Rate Management Contract [Member] | Designated as Hedging Instrument [Member] | Other Receivables [Member]
Derivative [Line Items]
Total derivatives, asset	37.6	19.9
Interest Rate Management Contract [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Total derivatives, asset	155.0	160.0
Interest Rate Management Contract [Member] | Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Derivative [Line Items]
Total derivatives, liabilities	0.4	0.0
Interest Rate Management Contract [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Total derivatives, liabilities	22.5	12.0
Interest Rate Management Contract [Member] | Hedges Not Designated [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Total derivatives, asset	3.7	0.0
Interest Rate Management Contract [Member] | Hedges Not Designated [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Total derivatives, liabilities	$ 0.8	$ 0.7