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ASSET RETIREMENT OBLIGATIONS - Fair Value Increases (Decreases) of the Funds (Details) - Securities held in the Funds - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Fair value increases (decreases) |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Fair value increases (decreases) of the Funds | $ 229 | $ 281 | $ (360)
Unrealized gains (losses) |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Fair value increases (decreases) of the Funds | 113 | 241 | (391)
Alabama Power | Fair value increases (decreases) |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Fair value increases (decreases) of the Funds | 143 | 157 | (171)
Alabama Power | Unrealized gains (losses) |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Fair value increases (decreases) of the Funds | 64 | 119 | (204)
Georgia Power | Fair value increases (decreases) |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Fair value increases (decreases) of the Funds | 86 | 124 | (189)
Georgia Power | Unrealized gains (losses) |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Fair value increases (decreases) of the Funds | $ 49 | $ 122 | $ (187)

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