Introduction - Schedule of Goodwill (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Goodwill [Line Items]
Goodwill	$ 5,161	$ 5,161
SOUTHERN Co GAS
Goodwill [Line Items]
Goodwill	5,015	5,015
SOUTHERN Co GAS | Gas distribution operations
Goodwill [Line Items]
Goodwill	4,034	4,034
SOUTHERN Co GAS | Gas marketing services
Goodwill [Line Items]
Goodwill	$ 981	$ 981