Introduction - Schedule of Amortization of Other Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 8	$ 9	$ 16	$ 18
Decrease in operating revenues	5	5	10	10
SOUTHERN POWER CO
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	5	5	10	10
SOUTHERN Co GAS
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 1	$ 1	$ 3	$ 3