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Segment and Related Information - Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($) state	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) segment state	Jun. 30, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of states in which entity operates \| state	3		3
Operating revenues	$ 6,226	$ 5,422	$ 12,486	$ 12,319
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	$ 731	316	$ 1,146	611
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of states in which entity operates \| state	4		4
Operating revenues	$ 1,063	1,349	$ 3,105	4,325
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%
SOUTHERN Co GAS \| PennEast Pipeline
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	20.00%		20.00%
Traditional Electric Operating Companies \| Wholesale revenues, affiliates \| SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	$ 232	112	$ 337	193
SOUTHERN POWER CO \| Natural gas \| SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		$ 6		$ 18