Income Taxes (Unrecognized Tax Benefits - Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosures [Line Items]
Unrecognized tax benefits that would impact effective tax rate	$ 150.5
Unrecognized tax benefits	194.8	$ 101.0	$ 96.5	$ 103.5
Interest and penalties related to unrecognized tax benefits	(0.2)	1.8	$ 5.0
Accrued interest and penalties	$ 27.8	$ 28.5

Income Tax Disclosures [Line Items]

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 217
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15A
-Subparagraph (a)
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-Name Accounting Standards Codification
-Section 45
-Paragraph 10B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482525/740-10-45-10B

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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- Definition

The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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