VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Provision for uncollectible accounts:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 71	$ 78	$ 118
Charged to Income	87	71	51
Charged to Other Accounts	3	(1)	(23)
Deductions	93	77	68
Balance at End of Period	68	71	78	$ 118
Provision for uncollectible accounts: | Alabama Power
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	14	14	43
Charged to Income	16	10	(7)
Charged to Other Accounts	0	0	0
Deductions	14	10	22
Balance at End of Period	16	14	14	43
Provision for uncollectible accounts: | Georgia Power
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	3	2	26
Charged to Income	26	21	16
Charged to Other Accounts	0	0	(23)	23
Deductions	25	20	17
Balance at End of Period	4	3	2	26
Provision for uncollectible accounts: | Mississippi Power
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	1	1	1
Charged to Income	2	1	1
Charged to Other Accounts	0	1	0
Deductions	2	2	1
Balance at End of Period	1	1	1	1
Provision for uncollectible accounts: | Southern Power
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	1	5	0
Charged to Income	0	(2)	5
Charged to Other Accounts	0	0	0
Deductions	0	2	0
Balance at End of Period	1	1	5	0
Provision for uncollectible accounts: | Southern Company Gas
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	50	39	40
Charged to Income	43	55	26
Charged to Other Accounts	3	0	0
Deductions	52	44	27
Balance at End of Period	44	50	39	40
Tax valuation allowance (net state)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	207	169	112
Charged to Income	(14)	68	57
Charged to Other Accounts	(25)	(30)	0
Deductions	0	0	0
Balance at End of Period	168	207	169	112
Tax valuation allowance (net state) | Georgia Power
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	98	58	28
Charged to Income	(15)	70	30
Charged to Other Accounts	(23)	(30)	0
Deductions	0	0	0
Balance at End of Period	60	98	58	28
Tax valuation allowance (net state) | Mississippi Power
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	32	32	32
Charged to Income	0	0	0
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Balance at End of Period	32	32	32	32
Tax valuation allowance (net state) | Southern Power
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	21	21	27
Charged to Income	0	0	(6)
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Balance at End of Period	21	21	21	27
Tax valuation allowance (net state) | Southern Company Gas
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	7	7	4
Charged to Income	0	0	3
Charged to Other Accounts	(2)	0	0
Deductions	0	0	0
Balance at End of Period	$ 5	$ 7	$ 7	$ 4