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Derivatives - Schedule of Pre-tax Effects of Unrealized Derivative Gains (Losses) (Details) - Energy-related derivatives - USD ($) $ in Millions | Jun. 30, 2024 | Dec. 31, 2023
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Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | $ (149) | $ (257)
Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (123) | (180)
Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (42) | (87)
Other regulatory liabilities, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 14 | 9
Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 2 | 1
ALABAMA POWER CO |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (51) | (95)
ALABAMA POWER CO | Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (45) | (67)
ALABAMA POWER CO | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (15) | (32)
ALABAMA POWER CO | Other regulatory liabilities, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 8 | 4
ALABAMA POWER CO | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 1 | 0
GEORGIA POWER CO |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (64) | (112)
GEORGIA POWER CO | Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (53) | (80)
GEORGIA POWER CO | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (12) | (33)
GEORGIA POWER CO | Other regulatory liabilities, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 0 | 0
GEORGIA POWER CO | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 1 | 1
MISSISSIPPI POWER CO |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (31) | (46)
MISSISSIPPI POWER CO | Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (17) | (25)
MISSISSIPPI POWER CO | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (15) | (22)
MISSISSIPPI POWER CO | Other regulatory liabilities, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 1 | 1
MISSISSIPPI POWER CO | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | 0 | 0
SOUTHERN Co GAS |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (3) | (4)
SOUTHERN Co GAS | Other regulatory assets, current |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | (8) | (8)
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) | 5 | 4
SOUTHERN Co GAS | Other regulatory assets, deferred |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total energy-related derivative gains (losses) | $ 0 | $ 0

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