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DERIVATIVES - Schedule of Unrealized Gain (Loss) Recognized in the Balance Sheet (Details) - Energy-related derivatives - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | $ 155 | $ 12
Other regulatory assets, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | (17) |
Other regulatory assets, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) |  | (2)
Other regulatory liabilities, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 107 | 12
Other regulatory liabilities, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 65 | 2
Alabama Power |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 44 | 6
Alabama Power | Other regulatory assets, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | (6) |
Alabama Power | Other regulatory assets, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) |  | 0
Alabama Power | Other regulatory liabilities, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 28 | 5
Alabama Power | Other regulatory liabilities, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 22 | 1
Georgia Power |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 67 | 2
Georgia Power | Other regulatory assets, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 0 |
Georgia Power | Other regulatory assets, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) |  | (1)
Georgia Power | Other regulatory liabilities, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 48 | 2
Georgia Power | Other regulatory liabilities, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 19 | 1
Mississippi Power |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 51 | 0
Mississippi Power | Other regulatory assets, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 0 |
Mississippi Power | Other regulatory assets, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) |  | (1)
Mississippi Power | Other regulatory liabilities, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 27 | 1
Mississippi Power | Other regulatory liabilities, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 24 | 0
Southern Company Gas |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | (7) | 4
Southern Company Gas | Other regulatory assets, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | (11) |
Southern Company Gas | Other regulatory assets, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) |  | 0
Southern Company Gas | Other regulatory liabilities, current |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | 4 | 4
Southern Company Gas | Other regulatory liabilities, deferred |  |
Derivatives, Fair Value [Line Items] |  |
Total energy-related derivative gains (losses) | $ 0 | $ 0

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