Consolidated Comprehensive Income Statements (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Tax effect on translation adjustments	$ (29.4)	$ 25.1	$ 1.1
Tax effect on net gain (loss) on derivatives	23.7
Tax effect on net gain (loss) on derivatives		(1.5)	9.7
Tax effect on pension and postretirement benefits	(15.6)	(97.9)	55.2
Tax effect on derivatives reclassification adjustments	(17.7)
Tax effect on derivatives reclassification adjustments		4.5	(9.2)
Tax effect on pension and postretirement benefits reclassification adjustments	$ 27.1	$ 20.5	$ 44.9

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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Amount, before reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount, before reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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