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Derivatives - Narrative (Details) MMBTU in Millions | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 30, 2023 USD ($) | Jun. 30, 2022 USD ($) | Jun. 30, 2023 USD ($) MMBTU | Jun. 30, 2022 USD ($) | Jun. 30, 2024 USD ($) | Dec. 31, 2022 USD ($)
Derivative [Line Items] |  |  |  |  |  |
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU |  |  | 11 |  |  |
Collateral already posted, assets, aggregate fair value | $ 52,000,000 |  | $ 52,000,000 |  |  |
Derivatives | 693,000,000 |  | 693,000,000 |  |  | $ 617,000,000
Gain (Loss) Recognized in OCI on Derivatives | 36,000,000 | $ (61,000,000) | (50,000,000) | $ (34,000,000) |  |
Scenario, Forecast |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Energy-related derivative hedge gain (loss) to be reclassified within twelve months |  |  |  |  | $ 33,000,000 |
Interest rate derivatives |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivatives | 65,000,000 |  | 65,000,000 |  |  |
Interest rate derivatives | Scenario, Forecast |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Cash flow hedge gain (loss) to be reclassified within twelve months |  |  |  |  | (15,000,000) |
Interest rate derivatives | Cash Flow Hedging |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | 3,000,000 | 21,000,000 | (10,000,000) | 30,000,000 |  |
Energy-related derivatives | Not Designated as Hedging Instrument [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative instruments not designated as hedging instruments, gain (loss), net | 16,000,000 | (40,000,000) | 29,000,000 | (18,000,000) |  |
Energy-related derivatives | Cash Flow Hedging |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (5,000,000) | (1,000,000) | $ (50,000,000) | 41,000,000 |  |
SOUTHERN POWER CO |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU |  |  | 3 |  |  |
Foreign currency cash flow hedge gain (loss to be reclassified | 11,000,000 |  | $ 11,000,000 |  |  |
Collateral already posted, assets, aggregate fair value | 15,000,000 |  | 15,000,000 |  |  |
Derivatives | 37,000,000 |  | 37,000,000 |  |  | 59,000,000
Gain (Loss) Recognized in OCI on Derivatives | 6,000,000 | (72,000,000) | (4,000,000) | (95,000,000) |  |
SOUTHERN POWER CO | Scenario, Forecast |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Energy-related derivative hedge gain (loss) to be reclassified within twelve months |  |  |  |  | 9,000,000 |
SOUTHERN POWER CO | Interest rate derivatives |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivatives | 13,000,000 |  | 13,000,000 |  |  |
SOUTHERN POWER CO | Interest rate derivatives | Scenario, Forecast |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Cash flow hedge gain (loss) to be reclassified within twelve months |  |  |  |  | 0 |
SOUTHERN POWER CO | Energy-related derivatives | Not Designated as Hedging Instrument [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative instruments not designated as hedging instruments, gain (loss), net | 0 | 0 | 0 | 0 |  |
SOUTHERN POWER CO | Energy-related derivatives | Cash Flow Hedging |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (2,000,000) | 2,000,000 | (13,000,000) | 7,000,000 |  |
SOUTHERN Co GAS |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Collateral already posted, assets, aggregate fair value | 52,000,000 |  | 52,000,000 |  |  | 41,000,000
Derivatives | 110,000,000 |  | 110,000,000 |  |  | 110,000,000
Gain (Loss) Recognized in OCI on Derivatives | 0 | (7,000,000) | (33,000,000) | 30,000,000 |  |
SOUTHERN Co GAS | Scenario, Forecast |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Energy-related derivative hedge gain (loss) to be reclassified within twelve months |  |  |  |  | 24,000,000 |
SOUTHERN Co GAS | Interest rate derivatives | Scenario, Forecast |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Cash flow hedge gain (loss) to be reclassified within twelve months |  |  |  |  | 0 |
SOUTHERN Co GAS | Interest rate derivatives | Cash Flow Hedging |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | 3,000,000 | (5,000,000) | 4,000,000 | (5,000,000) |  |
SOUTHERN Co GAS | Energy-related derivatives | Cash Flow Hedging |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (3,000,000) | (2,000,000) | $ (37,000,000) | 35,000,000 |  |
ALABAMA POWER CO |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU |  |  | 3 |  |  |
Collateral already posted, assets, aggregate fair value | 0 |  | $ 0 |  |  |
Derivatives | 64,000,000 |  | 64,000,000 |  |  | 15,000,000
ALABAMA POWER CO | Interest rate derivatives | Scenario, Forecast |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Cash flow hedge gain (loss) to be reclassified within twelve months |  |  |  |  | 0 |
ALABAMA POWER CO | Energy-related derivatives | Not Designated as Hedging Instrument [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative instruments not designated as hedging instruments, gain (loss), net | 0 | 0 | 0 | 0 |  |
ALABAMA POWER CO | Energy-related derivatives | Cash Flow Hedging |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | 0 | 0 | $ 0 | 0 |  |
GEORGIA POWER CO |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU |  |  | 4 |  |  |
Derivatives | 90,000,000 |  | $ 90,000,000 |  |  | 41,000,000
GEORGIA POWER CO | Interest rate derivatives | Scenario, Forecast |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Cash flow hedge gain (loss) to be reclassified within twelve months |  |  |  |  | 0 |
GEORGIA POWER CO | Interest rate derivatives | Cash Flow Hedging |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (1,000,000) | 19,000,000 | (3,000,000) | 31,000,000 |  |
GEORGIA POWER CO | Energy-related derivatives | Not Designated as Hedging Instrument [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative instruments not designated as hedging instruments, gain (loss), net | 0 | 0 | $ 0 | 0 |  |
MISSISSIPPI POWER CO |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints | MMBTU |  |  | 1 |  |  |
Derivatives | 36,000,000 |  | $ 36,000,000 |  |  | $ 15,000,000
MISSISSIPPI POWER CO | Interest rate derivatives | Scenario, Forecast |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Cash flow hedge gain (loss) to be reclassified within twelve months |  |  |  |  | $ 0 |
MISSISSIPPI POWER CO | Energy-related derivatives | Not Designated as Hedging Instrument [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative instruments not designated as hedging instruments, gain (loss), net | 0 | 0 | 0 | 0 |  |
MISSISSIPPI POWER CO | Energy-related derivatives | Cash Flow Hedging |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | 0 | $ 0 | 0 | $ 0 |  |
Registrants | Derivative Counterparties |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Collateral already posted, assets, aggregate fair value | $ 0 |  | $ 0 |  |  |

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