RETIREMENT BENEFITS AND ASSETS HELD IN TRUST Schedule of Net Defined Benefit Cost Components (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
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| Pension plans | ||||
| Defined Benefit Plan Disclosure [Line Items] | ||||
| Service cost | $ 2 | $ 2 | $ 7 | $ 6 |
| Interest cost | 2 | 1 | 5 | 5 |
| Expected return on plan assets | (2) | (2) | (7) | (6) |
| Net cost | 2 | 1 | 5 | 5 |
| Other Postretirement Benefits Plan | ||||
| Defined Benefit Plan Disclosure [Line Items] | ||||
| Service cost | 2 | 1 | 6 | 5 |
| Interest cost | 2 | 2 | 5 | 5 |
| Expected return on plan assets | (2) | (2) | (7) | (6) |
| Amortization of unrecognized gain | (2) | (1) | (4) | (4) |
| Net cost | $ 0 | $ 0 | $ 0 | $ 0 |
| X | ||||||||||
- 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 Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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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- 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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- Details
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