VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Provision for uncollectible accounts:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		$ 118	$ 49	$ 50
Charged to Income		51	78	68
Charged to Other Accounts		(23)	27	0
Deductions		68	36	69
Balance at End of Period		78	118	49
Tax valuation allowance (net state)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		112	113	100
Charged to Income		57	0	13
Charged to Other Accounts		0	0	0
Deductions		0	1	0
Balance at End of Period		169	112	113
Alabama Power | Provision for uncollectible accounts:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		43	22	10
Charged to Income		(7)	25	24
Charged to Other Accounts		0	0	0
Deductions		22	4	12
Balance at End of Period		14	43	22
Georgia Power | Provision for uncollectible accounts:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		26	2	2
Charged to Income		16	14	13
Charged to Other Accounts		(23)	23	0
Deductions		17	13	13
Balance at End of Period		2	26	2
Georgia Power | Tax valuation allowance (net state)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		28	28	33
Charged to Income		30	0	(5)
Charged to Other Accounts		0	0	0
Deductions		0	0	0
Balance at End of Period		58	28	28
Mississippi Power | Provision for uncollectible accounts:
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	2
Charged to Other Accounts		0	0	0
Deductions		1	1	2
Balance at End of Period		1	1	1
Mississippi Power | Tax valuation allowance (net state)
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
Southern Power | Provision for uncollectible accounts:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		0	0	0
Charged to Income		5	0	0
Charged to Other Accounts		0	0	0
Deductions		0	0	0
Balance at End of Period		5	0	0
Southern Power | Tax valuation allowance (net state)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		27	29	22
Charged to Income		(6)	(1)	7
Charged to Other Accounts		0	0	0
Deductions		0	1	0
Balance at End of Period		21	27	29
Southern Company Gas | Provision for uncollectible accounts:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		40	18	30
Charged to Income		26	35	29
Charged to Other Accounts		0	4	0
Deductions		27	17	41
Balance at End of Period		39	40	18
Southern Company Gas | Tax valuation allowance (net state)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		4	4	12
Charged to Income		3	0	(8)
Charged to Other Accounts		0	0	0
Deductions		0	0	0
Balance at End of Period		7	$ 4	4
Triton | Southern Company Gas
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reversal of federal income tax valuation allowance	$ 13			13
State and Local Jurisdiction | Georgia Power
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowance		$ 58
State and Local Jurisdiction | Southern Company Gas
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowance				$ 5