Segment and Related Information - Narrative (Details) $ in Millions	3 Months Ended
Mar. 31, 2023 USD ($) state segment	Mar. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of states in which entity operates \| state	3
Operating revenues	$ 6,241	$ 6,258
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	$ 405	413
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of states in which entity operates \| state	4
Operating revenues	$ 1,829	2,043
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%
SOUTHERN Co GAS \| Dalton Pipeline
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	50.00%
Traditional Electric Operating Companies \| Wholesale revenues, affiliates \| SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	$ 135	$ 105

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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