Derivatives - Schedule of Pre-Tax Effects of Hedging on AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	$ (15)	$ 46	$ (19)	$ 65
Cash Flow Hedging \| Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(8)	(13)	1	6
Cash Flow Hedging \| Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	0	9	0	5
Cash Flow Hedging \| Foreign currency derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(7)	47	(19)	67
Fair Value Hedging \| Foreign currency derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Amount excluded from effectiveness testing recognized in earnings	0	3	(1)	(13)
GEORGIA POWER CO \| Cash Flow Hedging \| Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	0	5	0	3
SOUTHERN POWER CO
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(9)	46	(19)	69
SOUTHERN POWER CO \| Cash Flow Hedging \| Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(2)	(1)	0	2
SOUTHERN POWER CO \| Cash Flow Hedging \| Foreign currency derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(7)	47	(19)	67
SOUTHERN Co GAS
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(4)	(8)	3	8
SOUTHERN Co GAS \| Cash Flow Hedging \| Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(4)	(12)	3	4
SOUTHERN Co GAS \| Cash Flow Hedging \| Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	0	4	0	4
ALABAMA POWER CO \| Cash Flow Hedging \| Energy-related derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	$ (2)	$ 0	$ (2)	$ 0