DERIVATIVES - Derivative Financial Statement Presentation and Amounts With Balance Sheet Offsetting (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	$ 211	$ 238
Derivative asset, gross amount offset	(70)	(25)
Derivative asset, net amounts recognized in the balance sheets	141	213
Derivative liability, gross amounts recognized	728	153
Derivative liability, gross amounts offset	(111)	(28)
Derivative liability, gross amounts recognized in balance sheets	$ 617	$ 125
Derivative asset, statement of financial position, extensible enumeration, not disclosed, flag	Net amounts recognized in the Balance Sheets(b)	Net amounts recognized in the Balance Sheets(b)
Collateral already posted, aggregate fair value	$ 41
Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	15	$ 10
Derivative liability, gross amounts recognized	14	4
Energy-related derivatives | Other deferred charges and assets | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	2	1
Energy-related derivatives | Other deferred credits and liabilities | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	1	0
Energy-related derivatives | Assets from risk management activities | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	13	9
Energy-related derivatives | Other current liabilities | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	13	4
Interest rate derivatives
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized in balance sheets	78
Alabama Power
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amount offset	(24)	(5)
Derivative asset, net amounts recognized in the balance sheets	38	50
Derivative liability, gross amounts offset	(24)	(5)
Derivative liability, gross amounts recognized in balance sheets	15	6
Collateral already posted, aggregate fair value	0
Georgia Power
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	42	75
Derivative asset, gross amount offset	(21)	(8)
Derivative asset, net amounts recognized in the balance sheets	21	67
Derivative liability, gross amounts recognized	62	8
Derivative liability, gross amounts offset	(21)	(8)
Derivative liability, gross amounts recognized in balance sheets	41	0
Georgia Power | Energy-related derivatives | Other deferred charges and assets | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	0	0
Georgia Power | Energy-related derivatives | Other deferred credits and liabilities | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	1	0
Mississippi Power
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amount offset	(17)	(4)
Derivative asset, net amounts recognized in the balance sheets	42	52
Derivative liability, gross amounts offset	(17)	(4)
Derivative liability, gross amounts recognized in balance sheets	15	1
Southern Power
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, net amounts recognized in the balance sheets	8	4
Derivative liability, gross amounts recognized in balance sheets	59	16
Collateral already posted, aggregate fair value	15
Southern Power | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	3	1
Derivative liability, gross amounts recognized	0	0
Southern Power | Energy-related derivatives | Other current liabilities | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	0	0
Southern Power | Energy-related derivatives | Other current assets | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	2	1
Southern Power | Interest rate derivatives
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized in balance sheets	23
Southern Company Gas
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	28	35
Derivative asset, gross amount offset	0	(8)
Derivative asset, net amounts recognized in the balance sheets	28	27
Derivative liability, gross amounts recognized	151	27
Derivative liability, gross amounts offset	(41)	(11)
Derivative liability, gross amounts recognized in balance sheets	110	16
Collateral already posted, aggregate fair value	41	3
Southern Company Gas | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	12	9
Derivative liability, gross amounts recognized	13	4
Southern Company Gas | Energy-related derivatives | Other deferred charges and assets | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	1	1
Southern Company Gas | Energy-related derivatives | Other deferred credits and liabilities | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	1	0
Southern Company Gas | Energy-related derivatives | Assets from risk management activities | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	11	8
Southern Company Gas | Energy-related derivatives | Other current liabilities | Not Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	12	4
Hedging Instruments for Regulatory Purposes | Energy-related derivatives | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	175	201
Derivative liability, gross amounts recognized	165	36
Hedging Instruments for Regulatory Purposes | Energy-related derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	52	72
Hedging Instruments for Regulatory Purposes | Energy-related derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	44	6
Hedging Instruments for Regulatory Purposes | Energy-related derivatives | Assets from risk management activities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	123	129
Hedging Instruments for Regulatory Purposes | Energy-related derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	121	30
Hedging Instruments for Regulatory Purposes | Alabama Power | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	62	55
Derivative liability, gross amounts recognized	39	11
Hedging Instruments for Regulatory Purposes | Alabama Power | Energy-related derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	20	25
Hedging Instruments for Regulatory Purposes | Alabama Power | Energy-related derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	18	2
Hedging Instruments for Regulatory Purposes | Alabama Power | Energy-related derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	21	9
Hedging Instruments for Regulatory Purposes | Alabama Power | Energy-related derivatives | Other current assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	42	30
Hedging Instruments for Regulatory Purposes | Georgia Power | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	42	75
Derivative liability, gross amounts recognized	61	8
Hedging Instruments for Regulatory Purposes | Georgia Power | Energy-related derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	6	21
Hedging Instruments for Regulatory Purposes | Georgia Power | Energy-related derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	18	2
Hedging Instruments for Regulatory Purposes | Georgia Power | Energy-related derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	43	6
Hedging Instruments for Regulatory Purposes | Georgia Power | Energy-related derivatives | Other current assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	36	54
Hedging Instruments for Regulatory Purposes | Mississippi Power | Energy-related derivatives | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	59	56
Derivative liability, gross amounts recognized	32	5
Hedging Instruments for Regulatory Purposes | Mississippi Power | Energy-related derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	26	26
Hedging Instruments for Regulatory Purposes | Mississippi Power | Energy-related derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	8	2
Hedging Instruments for Regulatory Purposes | Mississippi Power | Energy-related derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	24	3
Hedging Instruments for Regulatory Purposes | Mississippi Power | Energy-related derivatives | Other current assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	33	30
Hedging Instruments for Regulatory Purposes | Southern Power | Energy-related derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	1	0
Hedging Instruments for Regulatory Purposes | Southern Power | Energy-related derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	0	0
Hedging Instruments for Regulatory Purposes | Southern Company Gas | Energy-related derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	1	0
Hedging Instruments for Regulatory Purposes | Southern Company Gas | Energy-related derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	4	0
Hedging Instruments for Regulatory Purposes | Southern Company Gas | Energy-related derivatives | Assets from risk management activities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	12	15
Hedging Instruments for Regulatory Purposes | Southern Company Gas | Energy-related derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	33	12
Cash Flow and Fair Value Hedging | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	21	27
Derivative liability, gross amounts recognized	549	113
Cash Flow and Fair Value Hedging | Energy-related derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	6	1
Cash Flow and Fair Value Hedging | Energy-related derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	4	0
Cash Flow and Fair Value Hedging | Energy-related derivatives | Assets from risk management activities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	3	7
Cash Flow and Fair Value Hedging | Energy-related derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	27	5
Cash Flow and Fair Value Hedging | Interest rate derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	0	0
Cash Flow and Fair Value Hedging | Interest rate derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	240	29
Cash Flow and Fair Value Hedging | Interest rate derivatives | Assets from risk management activities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	12	19
Cash Flow and Fair Value Hedging | Interest rate derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	62	0
Cash Flow and Fair Value Hedging | Foreign currency derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	0	0
Cash Flow and Fair Value Hedging | Foreign currency derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	182	40
Cash Flow and Fair Value Hedging | Foreign currency derivatives | Assets from risk management activities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	0	0
Cash Flow and Fair Value Hedging | Foreign currency derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	34	39
Cash Flow and Fair Value Hedging | Southern Power | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	5	3
Derivative liability, gross amounts recognized	59	16
Cash Flow and Fair Value Hedging | Southern Power | Energy-related derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	5	1
Cash Flow and Fair Value Hedging | Southern Power | Energy-related derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	0	0
Cash Flow and Fair Value Hedging | Southern Power | Energy-related derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	12	0
Cash Flow and Fair Value Hedging | Southern Power | Energy-related derivatives | Other current assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	0	2
Cash Flow and Fair Value Hedging | Southern Power | Foreign currency derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	0	0
Cash Flow and Fair Value Hedging | Southern Power | Foreign currency derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	36	0
Cash Flow and Fair Value Hedging | Southern Power | Foreign currency derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	11	16
Cash Flow and Fair Value Hedging | Southern Power | Foreign currency derivatives | Other current assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	0	0
Cash Flow and Fair Value Hedging | Southern Company Gas | Energy-related derivatives | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	4	11
Derivative liability, gross amounts recognized	105	11
Cash Flow and Fair Value Hedging | Southern Company Gas | Energy-related derivatives | Assets from risk management activities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	3	5
Cash Flow and Fair Value Hedging | Southern Company Gas | Energy-related derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	15	5
Cash Flow and Fair Value Hedging | Southern Company Gas | Interest rate derivatives | Other deferred charges and assets | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	0	0
Cash Flow and Fair Value Hedging | Southern Company Gas | Interest rate derivatives | Other deferred credits and liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	72	6
Cash Flow and Fair Value Hedging | Southern Company Gas | Interest rate derivatives | Assets from risk management activities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative asset, gross amounts recognized	0	6
Cash Flow and Fair Value Hedging | Southern Company Gas | Interest rate derivatives | Other current liabilities | Designated as Hedging Instrument
Fair value of energy-related derivatives and interest rate derivatives
Derivative liability, gross amounts recognized	$ 14	$ 0