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Income Taxes (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	20.30%	19.00%
Unrecognized tax benefits	$ 380		$ 82
ALABAMA POWER CO
Income Tax Contingency [Line Items]
Sale of investment tax credit	$ 80
Effective tax (benefit) rate	23.00%	21.20%
Unrecognized tax benefits	$ 144		0
GEORGIA POWER CO
Income Tax Contingency [Line Items]
Sale of investment tax credit	64
Payment for PTCs	$ 121
Effective tax (benefit) rate	20.00%	18.70%
Unrecognized tax benefits	$ 188		$ 34
SOUTHERN POWER CO
Income Tax Contingency [Line Items]
Sale of investment tax credit	$ 19
Effective tax (benefit) rate	6.00%	14.40%
MISSISSIPPI POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	22.50%	20.00%
SOUTHERN Co GAS
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	23.50%	24.90%

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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