Income Taxes - Cash Paid for Taxes, Net of Refunds (Details) - USD ($) $ in Millions	6 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income tax payments, net of refunds	$ 710.1	$ 321.8

Amount, after refund, of cash paid to foreign, federal, state, and local jurisdictions as income tax.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-2A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-URI https://asc.fasb.org/1943274/2147482685/740-10-50-22

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI https://asc.fasb.org/1943274/2147482913/230-10-50-2

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