CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement Of Stockholders Equity [Abstract]
Employee pension and postretirement benefits, tax	$ 8.6	$ 14.9	$ 10.6
Cash dividends declared per share on common stock (in dollars per share)	$ 1.20	$ 1.08	$ 0.96

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 10
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