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Derivatives - Schedule of Pre-tax Effects of Unrealized Derivative Gains (Losses) (Details) - Energy-related derivatives - USD ($) $ in Millions | Jun. 30, 2023 | Dec. 31, 2022
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Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | $ (177) | $ 9
Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (141) | (71)
Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (71) | (23)
Other regulatory liabilities, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 29 | 72
Other regulatory liabilities, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 6 | 31
ALABAMA POWER CO |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (52) | 23
ALABAMA POWER CO | Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (37) | (8)
ALABAMA POWER CO | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (27) | (7)
ALABAMA POWER CO | Other regulatory liabilities, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 11 | 29
ALABAMA POWER CO | Other regulatory liabilities, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 1 | 9
GEORGIA POWER CO |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (87) | (19)
GEORGIA POWER CO | Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (60) | (26)
GEORGIA POWER CO | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (30) | (14)
GEORGIA POWER CO | Other regulatory liabilities, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 2 | 19
GEORGIA POWER CO | Other regulatory liabilities, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 1 | 2
MISSISSIPPI POWER CO |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (28) | 27
MISSISSIPPI POWER CO | Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (22) | (13)
MISSISSIPPI POWER CO | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (14) | (2)
MISSISSIPPI POWER CO | Other regulatory liabilities, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 4 | 22
MISSISSIPPI POWER CO | Other regulatory liabilities, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 4 | 20
SOUTHERN Co GAS |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (10) | (22)
SOUTHERN Co GAS | Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (22) | (24)
SOUTHERN Co GAS | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 0 | 0
SOUTHERN Co GAS | Other regulatory liabilities, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 12 | 2
SOUTHERN Co GAS | Other regulatory liabilities, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | $ 0 | $ 0

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