Derivative Instruments and Hedging Activities - Schedule of Gross and Net Amounts of Derivative Instruments and Other Amounts (Details) - USD ($) $ in Millions |
Jun. 30, 2026 |
Sep. 30, 2025 |
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| Derivative Instruments and Hedging Activities Disclosure [Abstract] | ||
| Gross amount recognized, assets | $ 34 | $ 37 |
| Gross amount eligible for offsetting, assets | (12) | (10) |
| Net amount, assets | 22 | 27 |
| Gross amount recognized, liabilities | 12 | 14 |
| Gross amount eligible for offsetting, liabilities | (12) | (10) |
| Net amount, liabilities | $ 0 | $ 4 |
| X | ||||||||||
- Definition Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Fair value, after offset of derivative liability, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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