VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Millions	12 Months Ended
	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	$ 78	$ 118	$ 49
Charged to Income	71	51	78
Charged to Other Accounts	(1)	(23)	27
Deductions	77	68	36
Balance at End of Period	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	43	22
Charged to Income	10	(7)	25
Charged to Other Accounts	0	0	0
Deductions	10	22	4
Balance at End of Period	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	2	26	2
Charged to Income	21	16	14
Charged to Other Accounts	0	(23)	23
Deductions	20	17	13
Balance at End of Period	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	1	1	1
Charged to Other Accounts	1	0	0
Deductions	2	1	1
Balance at End of Period	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	5	0	0
Charged to Income	(2)	5	0
Charged to Other Accounts	0	0	0
Deductions	2	0	0
Balance at End of Period	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	39	40	18
Charged to Income	55	26	35
Charged to Other Accounts	0	0	4
Deductions	44	27	17
Balance at End of Period	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	169	112	113
Charged to Income	68	57	0
Charged to Other Accounts	(30)	0	0
Deductions	0	0	1
Balance at End of Period	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	58	28	28
Charged to Income	70	30	0
Charged to Other Accounts	(30)	0	0
Deductions	0	0	0
Balance at End of Period	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
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	27	29
Charged to Income	0	(6)	(1)
Charged to Other Accounts	0	0	0
Deductions	0	0	1
Balance at End of Period	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	4	4
Charged to Income	0	3	0
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Balance at End of Period	$ 7	$ 7	$ 4