FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Assets:
Derivative asset	$ 45	$ 32
Liabilities:
Derivative liability	554	659
Collateral already posted, aggregate fair value	17	62
Recurring
Assets:
Cash equivalents and restricted cash	552	268
Other investments	48	44
Total	3,349	2,806
Liabilities:
Contingent consideration	19	19
Other	24
Total	659	776
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents and restricted cash	533	253
Other investments	9	9
Total	1,594	1,238
Liabilities:
Contingent consideration	3	3
Other	0
Total	8	49
Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents and restricted cash	19	15
Other investments	31	27
Total	1,557	1,382
Liabilities:
Contingent consideration	0	0
Other	13
Total	624	711
Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents and restricted cash	0	0
Other investments	8	8
Total	8	8
Liabilities:
Contingent consideration	16	16
Other	11
Total	27	16
Recurring \| Fair Value Measured at Net Asset Value Per Share (NAV)
Assets:
Total	190	178
Alabama Power
Assets:
Derivative asset	7	5
Liabilities:
Derivative liability	23	100
Collateral already posted, aggregate fair value	0
Alabama Power \| Recurring
Assets:
Cash equivalents and restricted cash	353	134
Other investments	31	27
Total	1,795	1,435
Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents and restricted cash	334	119
Other investments	0	0
Total	952	715
Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents and restricted cash	19	15
Other investments	31	27
Total	653	542
Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents and restricted cash	0	0
Other investments	0	0
Total	0	0
Alabama Power \| Recurring \| Fair Value Measured at Net Asset Value Per Share (NAV)
Assets:
Total	190	178
Georgia Power
Assets:
Derivative asset	4	2
Liabilities:
Derivative liability	27	113
Georgia Power \| Recurring
Assets:
Cash equivalents and restricted cash	35
Total	1,290	1,176
Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents and restricted cash	35
Total	453	371
Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents and restricted cash	0
Total	837	805
Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents and restricted cash	0
Total	0	0
Mississippi Power
Assets:
Derivative asset	2	1
Liabilities:
Derivative liability	17	47
Mississippi Power \| Recurring
Assets:
Cash equivalents and restricted cash		17
Total		32
Mississippi Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents and restricted cash		17
Total		17
Mississippi Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents and restricted cash		0
Total		15
Mississippi Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents and restricted cash		0
Total		0
Southern Power
Assets:
Derivative asset	4	3
Liabilities:
Derivative liability	51	27
Other		13
Collateral already posted, aggregate fair value	0
Southern Power \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Other		0
Southern Power \| Significant Other Observable Inputs (Level 2)
Liabilities:
Other		13
Southern Power \| Significant Unobservable Inputs (Level 3)
Liabilities:
Other		0
Southern Power \| Recurring
Assets:
Cash equivalents and restricted cash	51
Total	55
Liabilities:
Contingent consideration	19
Other	24
Total	94	59
Southern Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents and restricted cash	51
Total	51
Liabilities:
Contingent consideration	3
Other	0
Total	3	3
Southern Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents and restricted cash	0
Total	4
Liabilities:
Contingent consideration	0
Other	13
Total	64	40
Southern Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents and restricted cash	0
Total	0
Liabilities:
Contingent consideration	16
Other	11
Total	27	16
Southern Company Gas
Assets:
Derivative asset	28	21
Liabilities:
Derivative liability	84	87
Collateral already posted, aggregate fair value	17	62
Southern Company Gas \| Recurring
Assets:
Cash equivalents and restricted cash	22
Total	82	26
Liabilities:
Total	95	137
Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents and restricted cash	22
Total	38	9
Liabilities:
Total	5	46
Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents and restricted cash	0
Total	44	17
Liabilities:
Total	90	91
Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents and restricted cash	0
Total	0	0
Liabilities:
Total	0	0
Energy-related derivatives \| Recurring
Assets:
Derivative asset	89	55
Liabilities:
Derivative liability	129	358
Energy-related derivatives \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	12	6
Liabilities:
Derivative liability	5	46
Energy-related derivatives \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	77	49
Liabilities:
Derivative liability	124	312
Energy-related derivatives \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Alabama Power \| Recurring
Assets:
Derivative asset	26	15
Liabilities:
Derivative liability	42	110
Energy-related derivatives \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	26	15
Liabilities:
Derivative liability	42	110
Energy-related derivatives \| Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Georgia Power \| Recurring
Assets:
Derivative asset	19	13
Liabilities:
Derivative liability	42	124
Energy-related derivatives \| Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	19	13
Liabilities:
Derivative liability	42	124
Energy-related derivatives \| Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Mississippi Power \| Recurring
Assets:
Derivative asset	19	15
Liabilities:
Derivative liability	34	61
Energy-related derivatives \| Mississippi Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Mississippi Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	19	15
Liabilities:
Derivative liability	34	61
Energy-related derivatives \| Mississippi Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Southern Power \| Recurring
Assets:
Derivative asset	4	3
Liabilities:
Derivative liability		5
Energy-related derivatives \| Southern Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability		0
Energy-related derivatives \| Southern Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	4	3
Liabilities:
Derivative liability		5
Energy-related derivatives \| Southern Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability		0
Energy-related derivatives \| Southern Company Gas \| Recurring
Assets:
Derivative asset	21	9
Liabilities:
Derivative liability	11	58
Energy-related derivatives \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	12	6
Liabilities:
Derivative liability	5	46
Energy-related derivatives \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	9	3
Liabilities:
Derivative liability	6	12
Energy-related derivatives \| Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Recurring
Liabilities:
Derivative liability	269	264
Interest rate derivatives \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Recurring \| Significant Other Observable Inputs (Level 2)
Liabilities:
Derivative liability	269	264
Interest rate derivatives \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Southern Company Gas \| Recurring
Liabilities:
Derivative liability	84	79
Interest rate derivatives \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Liabilities:
Derivative liability	84	79
Interest rate derivatives \| Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability	0	0
Foreign currency derivatives \| Recurring
Liabilities:
Derivative liability	218	122
Foreign currency derivatives \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivative liability	0	0
Foreign currency derivatives \| Recurring \| Significant Other Observable Inputs (Level 2)
Liabilities:
Derivative liability	218	122
Foreign currency derivatives \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability	0	0
Foreign currency derivatives \| Southern Power \| Recurring
Liabilities:
Derivative liability	51	22
Contingent consideration		19
Foreign currency derivatives \| Southern Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivative liability	0	0
Contingent consideration		3
Foreign currency derivatives \| Southern Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Liabilities:
Derivative liability	51	22
Contingent consideration		0
Foreign currency derivatives \| Southern Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability	0	0
Contingent consideration		16
Domestic equity \| Recurring
Assets:
Nuclear decommissioning trusts	1,099	980
Domestic equity \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	849	764
Domestic equity \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	250	216
Domestic equity \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Domestic equity \| Alabama Power \| Recurring
Assets:
Nuclear decommissioning trusts	700	651
Domestic equity \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	459	443
Domestic equity \| Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	241	208
Domestic equity \| Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Domestic equity \| Georgia Power \| Recurring
Assets:
Nuclear decommissioning trusts	391	322
Domestic equity \| Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	390	321
Domestic equity \| Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	1	1
Domestic equity \| Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Domestic equity \| Southern Company Gas \| Recurring
Assets:
Non-qualified deferred compensation trusts	8	7
Domestic equity \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Non-qualified deferred compensation trusts	0	0
Domestic equity \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Non-qualified deferred compensation trusts	8	7
Domestic equity \| Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Non-qualified deferred compensation trusts	0	0
Foreign equity \| Recurring
Assets:
Nuclear decommissioning trusts	323	316
Foreign equity \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	148	145
Foreign equity \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	175	171
Foreign equity \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Alabama Power \| Recurring
Assets:
Nuclear decommissioning trusts	148	145
Foreign equity \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	148	145
Foreign equity \| Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Georgia Power \| Recurring
Assets:
Nuclear decommissioning trusts	174	170
Foreign equity \| Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	174	170
Foreign equity \| Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Southern Company Gas \| Recurring
Assets:
Non-qualified deferred compensation trusts	1	1
Foreign equity \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Non-qualified deferred compensation trusts	0	0
Foreign equity \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Non-qualified deferred compensation trusts	1	1
Foreign equity \| Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Non-qualified deferred compensation trusts	0	0
U.S. Treasury and government agency securities \| Recurring
Assets:
Nuclear decommissioning trusts	371	369
Investments, available for sale:	9
U.S. Treasury and government agency securities \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	0	0
Investments, available for sale:	2
U.S. Treasury and government agency securities \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	371	369
Investments, available for sale:	7
U.S. Treasury and government agency securities \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Investments, available for sale:	0
U.S. Treasury and government agency securities \| Alabama Power \| Recurring
Assets:
Nuclear decommissioning trusts	16	20
U.S. Treasury and government agency securities \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	0	0
U.S. Treasury and government agency securities \| Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	16	20
U.S. Treasury and government agency securities \| Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
U.S. Treasury and government agency securities \| Georgia Power \| Recurring
Assets:
Nuclear decommissioning trusts	355	349
U.S. Treasury and government agency securities \| Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	0	0
U.S. Treasury and government agency securities \| Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	355	349
U.S. Treasury and government agency securities \| Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:

FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Millions

Dec. 31, 2024

Dec. 31, 2023

Assets:

Derivative asset

$ 45

$ 32

Liabilities:

Derivative liability

554

659

Collateral already posted, aggregate fair value