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Segment and Related Information - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($) state	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) state segment	Sep. 30, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of states in which entity operates \| state	3		3
Operating revenues	$ 7,481	$ 7,107	$ 20,513	$ 18,886
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	$ 423	480	$ 1,143	1,248
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of states in which entity operates \| state	4		4
Operating revenues	$ 667	674	$ 3,117	3,338
Number of reportable segments \| segment			3
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%
Traditional Electric Operating Companies \| Wholesale revenues, affiliates \| SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	$ 102	156	$ 280	406
Traditional Electric Operating Companies \| Natural Gas \| SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	$ 0	$ 0	$ 0	$ 0