Income Taxes (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2026 |
Mar. 31, 2025 |
Sep. 30, 2025 |
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| Income Tax Disclosure [Abstract] | |||||
| Income tax expense | $ (209.4) | $ (248.0) | $ (406.0) | $ (506.0) | |
| Effective tax rate (percent) | 24.10% | 23.20% | 24.40% | 23.20% | |
| Valuation allowance for deferred income taxes | $ 14.6 | $ 14.6 | $ 14.6 | ||
| Deferred tax liability, net | 8.4 | 8.4 | 0.0 | ||
| Deferred tax asset, net | $ 0.0 | $ 0.0 | $ 44.5 | ||
| X | ||||||||||
- Definition Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, with jurisdictional netting. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences with jurisdictional netting. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- References No definition available.
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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