Segment and Related Information - Schedule of Financial Data for Products and Services (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Concentration Risk [Line Items]
Operating revenues	$ 8,378	$ 6,238	$ 22,232	$ 17,346
Gain on sale			41	171
Retail
Concentration Risk [Line Items]
Operating revenues	5,961	4,551	14,363	11,492
Wholesale Electric
Concentration Risk [Line Items]
Operating revenues	1,197	731	2,798	1,822
Natural Gas
Concentration Risk [Line Items]
Operating revenues	857	623	3,998	2,994
Electric Utilities
Concentration Risk [Line Items]
Operating revenues	7,427	5,527	17,943	14,051
Electric Utilities | Retail
Concentration Risk [Line Items]
Operating revenues	5,961	4,551	14,363	11,492
Electric Utilities | Wholesale Electric
Concentration Risk [Line Items]
Operating revenues	1,197	731	2,798	1,822
Electric Utilities | Other Revenue
Concentration Risk [Line Items]
Operating revenues	269	245	782	737
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	857	623	3,998	2,994
Southern Company Gas' Revenues | Gas Distribution Operations
Concentration Risk [Line Items]
Operating revenues	748	553	3,513	2,451
Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	0	0	0	188
Southern Company Gas' Revenues | Gas marketing services
Concentration Risk [Line Items]
Operating revenues	85	52	420	311
Southern Company Gas' Revenues | Other
Concentration Risk [Line Items]
Operating revenues	24	18	65	44
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	$ 857	623	3,998	2,994
Gain on sale			5	127
Southern Company Gas' Revenues | PennEast Pipeline
Concentration Risk [Line Items]
Asset impairment charges, net of tax		$ 67		67
Southern Company Gas' Revenues | Disposal Group, Disposed of by Sale | Sequent
Concentration Risk [Line Items]
Gain on sale			121
Asset impairment charges, net of tax			93
Deferred tax expense, increase from change in appointment rate			$ 85	85
Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues				188
Less Gross Gas Costs				3,783
Third Party Gross Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues				3,881
Intercompany Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues				90
Total Gross Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues				$ 3,971