Fair Value Measurements (Schedule of Recurring Fair Value Measurements) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Mar. 31, 2019	Sep. 30, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets at Fair Value	$ 136.6	$ 146.1
Total Liabilities at Fair Value	95.9	94.1
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets at Fair Value	0.0	0.0
Total Liabilities at Fair Value	0.0	0.0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets at Fair Value	136.6	146.1
Total Liabilities at Fair Value	95.9	94.1
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets at Fair Value	0.0	0.0
Total Liabilities at Fair Value	0.0	0.0
Forward Exchange Contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	93.5	68.8
Derivative liabilities	80.2	80.2
Forward Exchange Contracts \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Forward Exchange Contracts \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	93.5	68.8
Derivative liabilities	80.2	80.2
Forward Exchange Contracts \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Interest Rate Management Contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	43.1	77.3
Derivative liabilities	15.7	13.9
Interest Rate Management Contracts \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Interest Rate Management Contracts \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	43.1	77.3
Derivative liabilities	15.7	13.9
Interest Rate Management Contracts \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	$ 0.0	$ 0.0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial and nonfinancial obligations.

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