Contingencies and Regulatory Matters - Georgia Power (Details) $ in Millions		1 Months Ended			9 Months Ended		12 Months Ended
	Apr. 03, 2018 USD ($)	Feb. 29, 2020 USD ($)	Jun. 30, 2019 USD ($)	Oct. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2019	Dec. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Effective tax rate					22.70%	42.60%
Deferred income tax benefit					$ 286	$ (15)
GEORGIA POWER CO
Loss Contingencies [Line Items]
Customer refund					$ 330
Effective tax rate					25.50%	37.00%
Deferred income tax benefit	$ 700				$ 185	$ (328)
Customer refund liability in absence of base rate case	$ 185
Retail regulatory equity ratio					0.53
Under recovered fuel balance, threshold for interim fuel rider					$ 200
Annual accrual for incremental operating and maintenance costs of damage from major storms					30
GEORGIA POWER CO | Storm Damage
Loss Contingencies [Line Items]
Regulatory asset					311
GEORGIA POWER CO | Subsequent Event
Loss Contingencies [Line Items]
Customer refundable fees, refund payments				$ 130
GEORGIA POWER CO | Other current liabilities
Loss Contingencies [Line Items]
Under recovered fuel balance					105			$ 165
GEORGIA POWER CO | Maximum
Loss Contingencies [Line Items]
Retail regulatory equity ratio	0.55
GEORGIA POWER CO | Maximum | Subsequent Event | Loss from Catastrophes
Loss Contingencies [Line Items]
Estimated restoration costs				150
GEORGIA POWER CO | Minimum | Subsequent Event | Loss from Catastrophes
Loss Contingencies [Line Items]
Estimated restoration costs				$ 125
GEORGIA POWER CO | State (net of federal benefit)
Loss Contingencies [Line Items]
Effective tax rate	6.00%
GEORGIA POWER CO | Scenario, Forecast
Loss Contingencies [Line Items]
Customer refundable fees, refund payments		$ 105	$ 95
GEORGIA POWER CO | Scenario, Forecast | State (net of federal benefit)
Loss Contingencies [Line Items]
Effective tax rate							5.75%
Impact of Tax Reform Legislation | GEORGIA POWER CO
Loss Contingencies [Line Items]
Regulatory liabilities					$ 655