DERIVATIVES - Schedule of Unrealized Gain (Loss) Recognized in the Balance Sheet (Details) - Energy-related derivatives - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	$ 9	$ 155
Other regulatory assets, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(71)	(17)
Other regulatory assets, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(23)
Other regulatory liabilities, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	72	107
Other regulatory liabilities, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	31	65
Alabama Power
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	23	44
Alabama Power | Other regulatory assets, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(8)	(6)
Alabama Power | Other regulatory assets, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(7)
Alabama Power | Other regulatory liabilities, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	29	28
Alabama Power | Other regulatory liabilities, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	9	22
Georgia Power
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(19)	67
Georgia Power | Other regulatory assets, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(26)	0
Georgia Power | Other regulatory assets, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(14)
Georgia Power | Other regulatory liabilities, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	19	48
Georgia Power | Other regulatory liabilities, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	2	19
Mississippi Power
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	27	51
Mississippi Power | Other regulatory assets, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(13)	0
Mississippi Power | Other regulatory assets, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(2)
Mississippi Power | Other regulatory liabilities, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	22	27
Mississippi Power | Other regulatory liabilities, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	20	24
Southern Company Gas
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(22)	(7)
Southern Company Gas | Other regulatory assets, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	(24)	(11)
Southern Company Gas | Other regulatory assets, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	0
Southern Company Gas | Other regulatory liabilities, current
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	2	4
Southern Company Gas | Other regulatory liabilities, deferred
Derivatives, Fair Value [Line Items]
Total energy-related derivative gains (losses)	$ 0	$ 0