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FINANCING - Bank Credit Arrangements (Details) - USD ($) | Feb. 16, 2022 | Dec. 31, 2021
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Line of Credit Facility [Line Items] |  |
Expires, 2022 |  | $ 280,000,000
Expires, 2023 |  | 125,000,000
Expires, 2024 |  | 700,000,000
Expires, 2025 |  | 6,550,000,000
Total |  | 7,655,000,000
Unused |  | 7,594,000,000
Due within One Year |  | 280,000,000
Southern Company |  |
Line of Credit Facility [Line Items] |  |
Expires, 2022 |  | 0
Expires, 2023 |  | 0
Expires, 2024 |  | 0
Expires, 2025 |  | 2,000,000,000
Total |  | 2,000,000,000
Unused |  | 1,998,000,000
Due within One Year |  | 0
Alabama Power |  |
Line of Credit Facility [Line Items] |  |
Expires, 2022 |  | 0
Expires, 2023 |  | 0
Expires, 2024 |  | 550,000,000
Expires, 2025 |  | 700,000,000
Total |  | 1,250,000,000
Unused |  | 1,250,000,000
Due within One Year |  | 0
Georgia Power |  |
Line of Credit Facility [Line Items] |  |
Expires, 2022 |  | 0
Expires, 2023 |  | 0
Expires, 2024 |  | 0
Expires, 2025 |  | 1,750,000,000
Total |  | 1,750,000,000
Unused |  | 1,726,000,000
Due within One Year |  | 0
Mississippi Power |  |
Line of Credit Facility [Line Items] |  |
Expires, 2022 |  | 0
Expires, 2023 |  | 125,000,000
Expires, 2024 |  | 150,000,000
Expires, 2025 |  | 0
Total |  | 275,000,000
Unused |  | 275,000,000
Due within One Year |  | 0
Southern Power |  |
Line of Credit Facility [Line Items] |  |
Expires, 2022 |  | 0
Expires, 2023 |  | 0
Expires, 2024 |  | 0
Expires, 2025 |  | 600,000,000
Total |  | 600,000,000
Unused |  | 568,000,000
Due within One Year |  | 0
Southern Power | Continuing Letter of Credit Facility A |  |
Line of Credit Facility [Line Items] |  |
Expires, 2024 |  | 75,000,000
Unused |  | 8,000,000
Southern Power | Continuing Letter of Credit Facility B |  |
Line of Credit Facility [Line Items] |  |
Expires, 2024 |  | 60,000,000
Unused |  | 4,000,000
Southern Power | Continuing Letter of Credit Facility B | Subsequent Event |  |
Line of Credit Facility [Line Items] |  |
Expires, 2025 | $ 75,000,000 |
Southern Company Gas |  |
Line of Credit Facility [Line Items] |  |
Expires, 2022 |  | 250,000,000
Expires, 2023 |  | 0
Expires, 2024 |  | 0
Expires, 2025 |  | 1,500,000,000
Total |  | 1,750,000,000
Unused |  | 1,747,000,000
Due within One Year |  | 250,000,000
Other Subsidiaries |  |
Line of Credit Facility [Line Items] |  |
Expires, 2022 |  | 30,000,000
Expires, 2023 |  | 0
Expires, 2024 |  | 0
Expires, 2025 |  | 0
Total |  | 30,000,000
Unused |  | 30,000,000
Due within One Year |  | 30,000,000
Southern Company Gas Capital |  |
Line of Credit Facility [Line Items] |  |
Total |  | 800,000,000
Nicor Gas |  |
Line of Credit Facility [Line Items] |  |
Total |  | $ 700,000,000

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