CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Pension and other postretirement benefit plan adjustments tax (expense) benefit	$ (0.0)	$ (12.8)	$ (0.0)	$ (22.6)
Net change in unrealized gains and losses on cash flow hedges tax (expense) benefit	$ (0.2)	$ 2.1	$ 4.6	$ 10.6

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 10A
-Subparagraph (j)
-SubTopic 10
-Topic 220
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-10A

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
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-Topic 220
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-10A

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 12
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-Topic 220
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-URI https://asc.fasb.org/1943274/2147482790/220-10-45-12

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 810
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-Name Accounting Standards Codification
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
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-Name Accounting Standards Codification
-Section 45
-Paragraph 10A
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-10A

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