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INCOME TAXES - Narrative (Details) - USD ($) | Mar. 31, 2024 | Mar. 25, 2024 | Dec. 31, 2023 | Aug. 16, 2022 | May 31, 2022
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Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |  |  |  |
Operating loss carryforwards, not subject to expiration, net of tax |  |  |  | $ 1,000,000,000 |
Operating loss carryforwards, subject to expiration |  |  | $ 8,100,000,000 |  |
Deferred tax liabilities, net | $ 46,000,000 |  |  |  |
Reduction to OPIC | $ 797,000,000 |  |  |  |
North American Transmission Company II LLC | FET |  |  |  |  |
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |  |  |  |
Operating loss carryforwards, subject to expiration |  | $ 7,300,000,000 |  |  |
Sale of ownership interest by parent |  | 49.90% |  |  | 19.90%

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