Financial Instruments (Gains and Losses Recognized In Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Summary of Net Investment Hedge Activity [Abstract]
Tax effects	$ (2.8)	$ 29.4	$ (25.1)
Net Amount Recognized in OCI	267.3	233.4	$ (356.2)
Summary of Cash Flow Hedge Activity [Abstract]
Tax effects	9.0	(23.7)
Net Amount Recognized in OCI	3.3	43.5
Net Investment Hedges
Summary of Net Investment Hedge Activity [Abstract]
Total Amount Recognized in OCI	21.6	(114.2)
Tax effects	(5.5)	28.2
Net Amount Recognized in OCI	16.1	(86.0)
Net Investment Hedges \| Forward exchange contracts
Summary of Net Investment Hedge Activity [Abstract]
Total Amount Recognized in OCI	11.4	(15.9)
Net Investment Hedges \| Foreign currency debt
Summary of Net Investment Hedge Activity [Abstract]
Total Amount Recognized in OCI	18.1	(100.2)
Net Investment Hedges \| Cross currency interest rate swaps
Summary of Net Investment Hedge Activity [Abstract]
Total Amount Recognized in OCI	(7.9)	1.9
Cash Flow Hedges
Summary of Cash Flow Hedge Activity [Abstract]
Total Amount Recognized in OCI	(5.7)	67.2
Tax effects	9.0	(23.7)
Net Amount Recognized in OCI	3.3	43.5
Cash Flow Hedges \| Forward exchange contracts
Summary of Cash Flow Hedge Activity [Abstract]
Total Amount Recognized in OCI	12.7	116.6
Cash Flow Hedges \| Forward exchange contracts, excluded components
Summary of Cash Flow Hedge Activity [Abstract]
Total Amount Recognized in OCI	(11.7)	(15.2)
Cash Flow Hedges \| Other
Summary of Cash Flow Hedge Activity [Abstract]
Total Amount Recognized in OCI	$ (6.7)	$ (34.2)

Amount after tax, before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount of tax expense (benefit), before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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