CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net (losses) gains on derivative instruments, tax	$ 3.2	$ (0.8)	$ (0.5)
Reclassifications of net losses (gains) on derivative instruments, tax	(0.7)	(2.6)	4.1
Foreign currency translation adjustments, tax	(13.3)	(0.5)	(0.6)
Benefit plans, principally actuarial (losses) gains, tax	5.4	(5.2)	(3.8)
Reclassifications of benefit plans actuarial losses and net prior service benefit, tax	$ (0.5)	$ 1.1	$ (2.1)

Amount of tax expense (benefit), after 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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-SubTopic 10
-Section 45
-Paragraph 12
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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 for reclassification adjustment from accumulated other comprehensive (income) loss of defined benefit plan.

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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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