Segment and Related Information - Schedule of Financial Data for Products and Services (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Concentration Risk [Line Items]
Operating revenues	$ 6,648	$ 5,910
Retail
Concentration Risk [Line Items]
Operating revenues	3,613	3,342
Wholesale Electric
Concentration Risk [Line Items]
Operating revenues	664	545
Other
Concentration Risk [Line Items]
Operating revenues	177	170
Other revenues
Concentration Risk [Line Items]
Operating revenues	136	159
Less Gross Gas Costs	69	82
Natural Gas
Concentration Risk [Line Items]
Operating revenues	2,058	1,694
Electric Utilities
Concentration Risk [Line Items]
Operating revenues	4,509	4,117
Electric Utilities | Retail
Concentration Risk [Line Items]
Operating revenues	3,613	3,342
Electric Utilities | Wholesale Electric
Concentration Risk [Line Items]
Operating revenues	664	545
Electric Utilities | Other Revenue
Concentration Risk [Line Items]
Operating revenues	232	230
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	2,058	1,694
Southern Company Gas' Revenues | Gas Distribution Operations
Concentration Risk [Line Items]
Operating revenues	1,791	1,192
Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues	0	298
Southern Company Gas' Revenues | Gas marketing services
Concentration Risk [Line Items]
Operating revenues	243	195
Southern Company Gas' Revenues | Other
Concentration Risk [Line Items]
Operating revenues	24	9
Southern Company Gas' Revenues
Concentration Risk [Line Items]
Operating revenues	$ 2,058	1,694
Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues		298
Less Gross Gas Costs		2,353
Third Party Gross Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues		2,588
Intercompany Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues		63
Total Gross Revenues | Southern Company Gas' Revenues | Wholesale Gas Services
Concentration Risk [Line Items]
Operating revenues		$ 2,651