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FINANCING - Maturities of Long-Term Debt (Details) - USD ($) | Dec. 31, 2021 | Dec. 31, 2019
--- | --- | ---
Debt Instrument [Line Items] |  |
2022 | $ 2,157,000,000 |
2023 | 3,738,000,000 |
2024 | 2,280,000,000 |
2025 | 1,199,000,000 |
2026 | 3,723,000,000 |
Series 2019A Remarketable Junior Subordinated Notes | Junior subordinated notes |  |
Debt Instrument [Line Items] |  |
Debt instrument, face amount |  | $ 1,725,000,000
Alabama Power |  |
Debt Instrument [Line Items] |  |
2022 | 751,000,000 |
2023 | 301,000,000 |
2024 | 22,000,000 |
2025 | 250,000,000 |
2026 | 45,000,000 |
Georgia Power |  |
Debt Instrument [Line Items] |  |
2022 | 676,000,000 |
2023 | 897,000,000 |
2024 | 498,000,000 |
2025 | 145,000,000 |
2026 | 441,000,000 |
Mississippi Power |  |
Debt Instrument [Line Items] |  |
2022 | 1,000,000 |
2023 | 1,000,000 |
2024 | 201,000,000 |
2025 | 11,000,000 |
2026 | 1,000,000 |
Southern Power |  |
Debt Instrument [Line Items] |  |
2022 | 677,000,000 |
2023 | 290,000,000 |
2024 | 0 |
2025 | 500,000,000 |
2026 | 964,000,000 |
Southern Power | Euro-denominated Debt |  |
Debt Instrument [Line Items] |  |
2026 | 564,000,000 |
Southern Company Gas |  |
Debt Instrument [Line Items] |  |
2022 | 46,000,000 |
2023 | 400,000,000 |
2024 | 0 |
2025 | 300,000,000 |
2026 | $ 530,000,000 |

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