Segment and Related Information - Schedule of Financial Data for Products and Services (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Concentration Risk [Line Items]
Operating revenues	$ 6,980	$ 8,378	$ 19,208	$ 22,232
Electric Utilities
Concentration Risk [Line Items]
Operating revenues	6,167	7,427	15,414	17,943
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	689	857	3,417	3,998
Retail electric revenues
Concentration Risk [Line Items]
Operating revenues	5,139	5,961	12,597	14,363
Retail electric revenues | Electric Utilities
Concentration Risk [Line Items]
Operating revenues	5,139	5,961	12,597	14,363
Wholesale electric revenues
Concentration Risk [Line Items]
Operating revenues	727	1,197	1,930	2,798
Wholesale electric revenues | Electric Utilities
Concentration Risk [Line Items]
Operating revenues	727	1,197	1,930	2,798
Other Revenue | Electric Utilities
Concentration Risk [Line Items]
Operating revenues	301	269	887	782
Other electric revenues
Concentration Risk [Line Items]
Operating revenues	203	185	602	554
Natural Gas
Concentration Risk [Line Items]
Operating revenues	689	857	3,417	3,998
Gas Distribution Operations | Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	617	748	2,989	3,513
Gas marketing services | Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	56	85	376	420
Other | Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	16	24	52	65
Other revenues
Concentration Risk [Line Items]
Operating revenues	$ 222	$ 178	$ 662	$ 519