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Introduction - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025	Dec. 31, 2024
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and cash equivalents	$ 981	$ 1,639
Restricted cash:
Total cash, cash equivalents, and restricted cash	987	1,640	$ 2,332	$ 1,101
Other current assets
Restricted cash:
Restricted cash	6	1
GEORGIA POWER CO
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and cash equivalents	24	59
Restricted cash:
Total cash, cash equivalents, and restricted cash	24	59	383	118
SOUTHERN POWER CO
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and cash equivalents	72	105
Restricted cash:
Total cash, cash equivalents, and restricted cash	72	105	192	168
SOUTHERN Co GAS
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and cash equivalents	137	15
Restricted cash:
Total cash, cash equivalents, and restricted cash	142	15	$ 87	$ 44
SOUTHERN Co GAS \| Other current assets
Restricted cash:
Restricted cash	5	0
Southern Holdings Company \| Collateral For Life Insurance And Long-Term Disability Insurance
Restricted cash:
Restricted cash	$ 1	$ 1