Income Taxes - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	20.00%	17.50%
Unrecognized tax positions	$ 79		$ 47
ITC and PTC carryforwards
Income Tax Contingency [Line Items]
Deferred tax assets	$ 1,000		$ 1,200
GEORGIA POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	18.50%	7.30%
MISSISSIPPI POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	20.10%	14.30%
SOUTHERN POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	18.80%	(1.60%)
SOUTHERN Co GAS
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	23.70%	36.60%
Unrecognized tax positions	$ 32