Introduction - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 1,676	$ 1,917
Restricted cash:
Total cash, cash equivalents, and restricted cash	1,890	2,037	$ 2,013	$ 1,829
Other current assets
Restricted cash:
Restricted cash	176	62
Other deferred charges and assets
Restricted cash:
Restricted cash	38	58
ALABAMA POWER CO
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	621	687
Restricted cash:
Total cash, cash equivalents, and restricted cash	729	687	1,458	1,060
ALABAMA POWER CO | Other current assets
Restricted cash:
Restricted cash	108	0
ALABAMA POWER CO | Other deferred charges and assets
Restricted cash:
Restricted cash	0	0
GEORGIA POWER CO
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	173	364
Restricted cash:
Total cash, cash equivalents, and restricted cash	256	480	33	33
GEORGIA POWER CO | Other current assets
Restricted cash:
Restricted cash	48	60
GEORGIA POWER CO | Other deferred charges and assets
Restricted cash:
Restricted cash	35	56
SOUTHERN POWER CO
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	236	131
Restricted cash:
Total cash, cash equivalents, and restricted cash	257	133	231	135
SOUTHERN POWER CO | Other current assets
Restricted cash:
Restricted cash	18	0
SOUTHERN POWER CO | Other deferred charges and assets
Restricted cash:
Restricted cash	3	3
SOUTHERN POWER CO | Proceeds From Issuance Of Solid Waste Disposal Facility Revenue Bonds
Restricted cash:
Restricted cash	18
SOUTHERN POWER CO | Estimated Construction Completion Costs | Deuel Harvest
Restricted cash:
Restricted cash	3	3
SOUTHERN Co GAS
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	397	81
Restricted cash:
Total cash, cash equivalents, and restricted cash	399	83	$ 28	$ 48
SOUTHERN Co GAS | Other current assets
Restricted cash:
Restricted cash	2	2
SOUTHERN Co GAS | Other deferred charges and assets
Restricted cash:
Restricted cash	$ 0	$ 0