Income Taxes (Details) - USD ($) $ in Billions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	33.50%	(3.20%)
GEORGIA POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	21.70%	(53.50%)
MISSISSIPPI POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	14.00%	18.70%
SOUTHERN POWER CO
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	(35.50%)	(1386.50%)
SOUTHERN Co GAS
Income Tax Contingency [Line Items]
Effective tax (benefit) rate	18.00%	39.10%
Investment Tax Credit Carryforward
Income Tax Contingency [Line Items]
Federal ITC/PTC carryforward	$ 2.0		$ 2.4