Consolidated Comprehensive Income Statements (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Tax effect on translation adjustments	$ 22.6	$ 11.3	$ (1.6)	$ 0.5
Tax effect on net gain (loss) on derivatives	(13.2)	6.0	(10.5)	8.6
Tax effect on derivatives reclassification adjustments	12.0	(5.0)	11.2	(5.8)
Tax effect on pension and postretirement benefits reclassification adjustments	$ 5.9	$ 6.5	$ 11.8	$ 13.0

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 of tax expense (benefit) for reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount of tax (expense) benefit for reclassification adjustment from accumulated other comprehensive (income) loss of defined benefit plan.

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