Consolidated Comprehensive Income Statements (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Tax effect on translation adjustments	$ 25.1	$ 1.1	$ (19.3)
Tax effect on net gain (loss) on derivatives	(1.5)	9.7	(11.0)
Tax effect on pension and postretirement benefits	(97.9)	55.2	109.0
Tax effect on derivatives reclassification adjustments	4.5	(9.2)	11.7
Tax effect on pension and postretirement benefits reclassification adjustments	$ 20.5	$ 44.9	$ 50.7

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

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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Amount of tax expense (benefit), before reclassification adjustments, related to increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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