RETIREMENT BENEFITS - Components of Net Periodic Benefit Cost and Estimated Future Benefit Payments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pension plans
Components of net periodic
Service cost	$ 292	$ 275	$ 412
Interest cost	635	626	408
Expected return on plan assets	(1,263)	(1,229)	(1,265)
Recognized net loss(*)	55	32	240
Net amortization(*)	0	0	0
Prior service cost(*)	0	0	0
Total change	(281)	(296)	(205)
Benefit payments:
2025	773
2026	801
2027	823
2028	842
2029	862
2030 to 2034	4,529
Unamortized amounts	20	17	21
Other Postretirement Benefits Plan
Components of net periodic
Service cost	15	15	23
Interest cost	65	70	42
Expected return on plan assets	(89)	(83)	(80)
Prior service cost(*)	(13)	(11)	(1)
Total change	(22)	(9)	(16)
Benefit payments:
2025	112
2026	112
2027	113
2028	114
2029	114
2030 to 2034	558
Unamortized amounts	8
Alabama Power | Pension plans
Components of net periodic
Service cost	68	64	99
Interest cost	148	145	96
Expected return on plan assets	(307)	(297)	(306)
Recognized net loss(*)	16	9	62
Net amortization(*)	1	1	1
Prior service cost(*)	0	0	0
Total change	(74)	(78)	(48)
Benefit payments:
2025	170
2026	177
2027	183
2028	187
2029	192
2030 to 2034	1,013
Alabama Power | Other Postretirement Benefits Plan
Components of net periodic
Service cost	4	4	6
Interest cost	16	17	10
Expected return on plan assets	(35)	(33)	(32)
Prior service cost(*)	(3)	(3)	0
Total change	(18)	(15)	(16)
Benefit payments:
2025	24
2026	25
2027	26
2028	26
2029	27
2030 to 2034	133
Georgia Power | Pension plans
Components of net periodic
Service cost	70	68	103
Interest cost	191	191	123
Expected return on plan assets	(393)	(385)	(399)
Recognized net loss(*)	19	13	75
Net amortization(*)	1	1	1
Prior service cost(*)	0	0	0
Total change	(112)	(112)	(97)
Benefit payments:
2025	245
2026	250
2027	254
2028	258
2029	262
2030 to 2034	1,333
Georgia Power | Other Postretirement Benefits Plan
Components of net periodic
Service cost	4	4	6
Interest cost	23	25	15
Expected return on plan assets	(32)	(29)	(28)
Prior service cost(*)	(4)	(3)	2
Total change	(9)	(3)	(5)
Benefit payments:
2025	40
2026	40
2027	41
2028	41
2029	42
2030 to 2034	205
Mississippi Power | Pension plans
Components of net periodic
Service cost	12	11	17
Interest cost	29	28	18
Expected return on plan assets	(58)	(56)	(57)
Recognized net loss(*)	3	2	11
Net amortization(*)	0	0	0
Prior service cost(*)	0	0	0
Total change	(14)	(15)	(11)
Benefit payments:
2025	34
2026	36
2027	37
2028	38
2029	38
2030 to 2034	204
Mississippi Power | Other Postretirement Benefits Plan
Components of net periodic
Service cost	1	1	1
Interest cost	3	3	2
Expected return on plan assets	(3)	(3)	(2)
Prior service cost(*)	0	0	0
Total change	1	1	1
Benefit payments:
2025	5
2026	5
2027	5
2028	5
2029	5
2030 to 2034	22
Southern Power | Pension plans
Components of net periodic
Service cost	7	6	9
Interest cost	9	8	6
Expected return on plan assets	(17)	(15)	(15)
Recognized net loss(*)	0	0	2
Net amortization(*)	0	0	0
Prior service cost(*)	0	0	0
Total change	(1)	(1)	2
Benefit payments:
2025	7
2026	8
2027	8
2028	7
2029	8
2030 to 2034	51
Southern Power | Other Postretirement Benefits Plan
Components of net periodic
Service cost	0	0	0
Interest cost	0	0	0
Expected return on plan assets	1	1	1
Prior service cost(*)	0	0	0
Total change	1	1	1
Benefit payments:
2025	1
2026	1
2027	1
2028	1
2029	1
2030 to 2034	1
Southern Company Gas | Pension plans
Components of net periodic
Service cost	28	24	34
Interest cost	42	42	28
Expected return on plan assets	(85)	(85)	(91)
Recognized net loss(*)	0	(5)	8
Net amortization(*)	15	15	15
Prior service cost(*)	(3)	(3)	(3)
Total change	(3)	(12)	(9)
Benefit payments:
2025	58
2026	60
2027	62
2028	64
2029	66
2030 to 2034	346
Southern Company Gas | Other Postretirement Benefits Plan
Components of net periodic
Service cost	1	1	1
Interest cost	8	9	5
Expected return on plan assets	(13)	(10)	(9)
Prior service cost(*)	6	6	6
Total change	2	$ 6	$ 3
Benefit payments:
2025	16
2026	16
2027	15
2028	15
2029	14
2030 to 2034	$ 61