Consolidated Comprehensive Income Statements (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Tax effect on translation adjustments	$ (32.8)	$ 71.2	$ 2.8
Tax effect on net gain (loss) on derivatives	48.6	(63.9)	(9.0)
Tax effect on pension and postretirement benefits	(2.9)	(33.4)	91.4
Tax effect on derivatives reclassification adjustments	(13.6)	30.3	13.9
Tax effect on pension and postretirement benefits reclassification adjustments	$ 17.5	$ 21.8	$ 24.4

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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