FINANCING - Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Finance lease obligations	$ 768	$ 287
Unamortized fair value adjustment	249	275
Unamortized debt premium (discount), net	(56)	(58)
Unamortized debt issuance expense	(488)	(419)
Total long-term debt	71,869	63,486
Securities due within one year	6,220	4,718
Long-Term Debt	$ 65,649	58,768
Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.38%
Long-term debt, gross	$ 49,922	44,862
Junior subordinated notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.82%
Long-term debt, gross	$ 9,922	7,389
FFB loans
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.88%
Long-term debt, gross	$ 4,617	4,703
Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.14%
Long-term debt, gross	$ 3,323	3,379
First mortgage bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.93%
Long-term debt, gross	$ 2,925	2,775
Medium-term notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	7.03%
Long-term debt, gross	$ 84	84
Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.56%
Long-term debt, gross	$ 603	209
Alabama Power
Debt Instrument [Line Items]
Finance lease obligations	12	4
Unamortized debt premium (discount), net	(20)	(19)
Unamortized debt issuance expense	(69)	(67)
Total long-term debt	12,013	11,154
Securities due within one year	625	655
Long-Term Debt	$ 11,388	10,499
Alabama Power | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.02%
Long-term debt, gross	$ 10,725	9,875
Alabama Power | Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.11%
Long-term debt, gross	$ 1,300	1,300
Alabama Power | Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	5.32%
Long-term debt, gross	$ 65	61
Georgia Power
Debt Instrument [Line Items]
Finance lease obligations	734	261
Unamortized debt premium (discount), net	(17)	(21)
Unamortized debt issuance expense	(127)	(123)
Total long-term debt	21,492	18,350
Securities due within one year	1,370	966
Long-Term Debt	$ 20,122	17,384
Georgia Power | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.48%
Long-term debt, gross	$ 13,692	11,292
Georgia Power | Junior subordinated notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	5.00%
Long-term debt, gross	$ 270	270
Georgia Power | FFB loans
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.88%
Long-term debt, gross	$ 4,617	4,703
Georgia Power | Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.16%
Long-term debt, gross	$ 1,923	1,968
Georgia Power | Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.59%
Long-term debt, gross	$ 400	0
Mississippi Power
Debt Instrument [Line Items]
Finance lease obligations	19	14
Unamortized debt premium (discount), net	1	2
Unamortized debt issuance expense	(10)	(9)
Total long-term debt	1,786	1,693
Securities due within one year	66	12
Long-Term Debt	$ 1,720	1,681
Mississippi Power | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.40%
Long-term debt, gross	$ 1,675	1,575
Mississippi Power | Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.94%
Long-term debt, gross	$ 101	111
Southern Power
Debt Instrument [Line Items]
Finance lease obligations	0	0
Unamortized debt premium (discount), net	(6)	(4)
Unamortized debt issuance expense	(17)	(11)
Total long-term debt	2,940	2,680
Securities due within one year	587	500
Long-Term Debt	2,353	2,180
Fair value gain (loss)	$ 23	(45)
Southern Power | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.65%
Long-term debt, gross	$ 2,963	2,695
Southern Company Gas
Debt Instrument [Line Items]
Finance lease obligations	0	0
Unamortized fair value adjustment	249	275
Unamortized debt premium (discount), net	(11)	(9)
Unamortized debt issuance expense	(40)	(37)
Total long-term debt	9,274	8,531
Securities due within one year	531	302
Long-Term Debt	$ 8,743	8,229
Southern Company Gas | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.46%
Long-term debt, gross	$ 5,999	5,375
Southern Company Gas | First mortgage bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.93%
Long-term debt, gross	$ 2,925	2,775
Southern Company Gas | Medium-term notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	7.03%
Long-term debt, gross	$ 84	84
Southern Company Gas | Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.81%
Long-term debt, gross	$ 68	$ 68