Retirement Benefits - Schedule of Components of Net Periodic Benefit Cost (Income) (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2024 |
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| Amortization [Abstract] | |||
| Amortization of net actuarial loss (gain) | $ 18 | ||
| Pension Benefits | |||
| Components of net periodic benefit cost | |||
| Service cost | $ 38 | $ 41 | $ 37 |
| Interest cost | Other income (expense) | Other income (expense) | Other income (expense) |
| Interest cost | $ 137 | $ 136 | $ 147 |
| Expected return on plan assets | Other income (expense) | Other income (expense) | Other income (expense) |
| Expected return on plan assets | $ (170) | $ (167) | $ (170) |
| Amortization [Abstract] | |||
| Amortization of net actuarial loss (gain) | $ 16 | $ 27 | $ (1) |
| Settlement and curtailment charges | Other income (expense) | Other income (expense) | Other income (expense) |
| Settlement and curtailment charges | $ 11 | $ 1 | $ 0 |
| Net periodic benefit cost | 32 | 38 | 13 |
| Other Postretirement Benefits | |||
| Components of net periodic benefit cost | |||
| Service cost | $ 1 | $ 1 | $ 1 |
| Interest cost | Other income (expense) | Other income (expense) | Other income (expense) |
| Interest cost | $ 2 | $ 2 | $ 3 |
| Expected return on plan assets | Other income (expense) | Other income (expense) | Other income (expense) |
| Expected return on plan assets | $ 0 | $ 0 | $ 0 |
| Amortization [Abstract] | |||
| Amortization of net actuarial loss (gain) | $ 2 | $ 2 | $ 1 |
| Settlement and curtailment charges | Other income (expense) | Other income (expense) | Other income (expense) |
| Settlement and curtailment charges | $ 0 | $ 0 | $ 0 |
| Net periodic benefit cost | $ 5 | $ 5 | $ 5 |
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- References No definition available.
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of cost recognized for passage of time related to defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of net periodic benefit cost (credit) for defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- References No definition available.
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- Definition Indicates line item in statement of income or comprehensive income that includes expected return (loss) on plan asset component of net periodic benefit (cost) credit for defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Indicates line item in statement of income or comprehensive income that includes interest cost component of net periodic benefit cost (credit) for defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Indicates line item in statement of income or comprehensive income that includes settlement gain (loss) component of net periodic benefit (cost) credit for defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Details
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