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INCOME TAXES - Narrative (Details) - USD ($) $ in Millions | Dec. 31, 2025 | Mar. 31, 2024 | Mar. 25, 2024 | Dec. 31, 2023 | Aug. 16, 2022
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Provision For Income Tax [Line Items] |  |  |  |  |
Operating loss carryforwards, not subject to expiration, net of tax |  |  |  |  | $ 1,000
Deferred tax liabilities, net |  | $ 46 |  |  |
Reduction to OPIC |  | $ 803 |  |  |
Operating Loss Carryforwards |  |  |  | $ 8,100 |
Forecast |  |  |  |  |
Provision For Income Tax [Line Items] |  |  |  |  |
Operating loss carryforwards, subject to expiration | $ 1,600 |  |  |  |
North American Transmission Company II LLC | FET |  |  |  |  |
Provision For Income Tax [Line Items] |  |  |  |  |
Tax gain from combined sale |  |  | $ 7,000 |  |
Sale of ownership interest by parent |  | 19.90% | 49.90% |  |

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