Introduction - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and cash equivalents	$ 3,341	$ 1,070
Restricted cash:
Total cash, cash equivalents, and restricted cash	3,342	1,101	$ 1,055	$ 921
Other current assets
Restricted cash:
Restricted cash	1	31
GEORGIA POWER CO
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and cash equivalents	937	97
Restricted cash:
Total cash, cash equivalents, and restricted cash	937	118	64	75
GEORGIA POWER CO | Other current assets
Restricted cash:
Restricted cash	0	21
SOUTHERN POWER CO
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and cash equivalents	1,047	159
Restricted cash:
Total cash, cash equivalents, and restricted cash	1,047	168	195	144
SOUTHERN POWER CO | Other current assets
Restricted cash:
Restricted cash	0	9
SOUTHERN Co GAS
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and cash equivalents	346	43
Restricted cash:
Total cash, cash equivalents, and restricted cash	346	44	$ 45	$ 35
SOUTHERN Co GAS | Other current assets
Restricted cash:
Restricted cash	0	1
SOUTHERN Co GAS | Collateral For Life Insurance And Long-Term Disability Insurance
Restricted cash:
Restricted cash		$ 1
Southern Holdings Company | Collateral For Life Insurance And Long-Term Disability Insurance
Restricted cash:
Restricted cash	$ 1