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v3.25.3

Segment and Related Information - Narrative (Details) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 USD ($) state | Sep. 30, 2024 USD ($) | Sep. 30, 2025 USD ($) state segment | Sep. 30, 2024 USD ($)
Segment Reporting Information [Line Items] |  |  |  |
Number of states in which entity operates | state | 3 |  | 3 |
Operating revenues | $ 7,822 | $ 7,481 | $ 22,142 | $ 20,513
Earnings from equity method investments | 33 | 31 | 76 | 107
Other segment items | 3,564 | 3,491 | $ 11,377 | 10,146
Traditional Electric Operating Companies |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Number of operating segments | segment |  |  | 3 |
Number of reportable segments | segment |  |  | 1 |
SOUTHERN POWER CO |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Number of reportable segments | segment |  |  | 1 |
Operating revenues | 417 | 423 | $ 1,212 | 1,143
SOUTHERN POWER CO | Kay Wind Facility |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Depreciation before tax | 112 |  | 181 |
Depreciation after tax | 80 |  | 130 |
SOUTHERN POWER CO | Reportable Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Other segment items | $ 332 | 322 | $ 930 | 834
SOUTHERN Co GAS |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Number of states in which entity operates | state | 4 |  | 4 |
Number of reportable segments | segment |  |  | 3 |
Operating revenues | $ 725 | 667 | $ 3,537 | 3,117
Earnings from equity method investments | 31 | 34 | 93 | 110
Other segment items | $ 464 | 421 | $ 2,133 | 1,866
SOUTHERN Co GAS | Southern Natural Gas Company, LLC |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Ownership percentage, equity method investment | 50.00% |  | 50.00% |
SOUTHERN Co GAS | Dalton Pipeline |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Ownership percentage, equity method investment | 50.00% |  | 50.00% |
MISSISSIPPI POWER CO |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating revenues | $ 481 | 424 | $ 1,270 | 1,131
MISSISSIPPI POWER CO | Reportable Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Other segment items | 251 | 200 | 686 | 550
Traditional Electric Operating Companies | Wholesale revenues, affiliates | SOUTHERN POWER CO |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating revenues | 112 | 102 | 341 | 280
Traditional Electric Operating Companies | Natural Gas | SOUTHERN Co GAS |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating revenues | $ 0 | $ 0 | $ 0 | $ 0

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