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SEGMENT AND RELATED INFORMATION - Narrative (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2023 USD ($) segment state | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items] |  |  |
Total operating revenues | $ 25,253 | $ 29,279 | $ 23,113
Total operating revenues | 24,828 | 25,941 | 23,463
Southern Power |  |  |
Segment Reporting Information [Line Items] |  |  |
Total operating revenues | 2,189 | 3,369 | 2,216
Total operating revenues | 1,630 | 2,805 | 1,605
Southern Company Gas |  |  |
Segment Reporting Information [Line Items] |  |  |
Total operating revenues | 4,702 | 5,962 | 4,380
Total operating revenues | $ 4,598 | 5,905 | 6,293
Number of reportable segments | segment | 3 |  |
Number of states in which entity operates | state | 4 |  |
Southern Company Gas | Southern Power |  |  |
Segment Reporting Information [Line Items] |  |  |
Total operating revenues |  |  | 18
Southern Natural Gas Company, LLC | Southern Company Gas |  |  |
Segment Reporting Information [Line Items] |  |  |
Ownership percentage, equity method investment | 50.00% |  |
Dalton Pipeline | Southern Company Gas |  |  |
Segment Reporting Information [Line Items] |  |  |
Ownership percentage, equity method investment | 50.00% |  |
Wholesale revenues, affiliates | Southern Power | Traditional Electric Operating Companies |  |  |
Segment Reporting Information [Line Items] |  |  |
Total operating revenues | $ 537 | $ 875 | $ 515

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