Contingencies and Regulatory Matters - Nuclear Construction (Details) $ in Millions										3 Months Ended	12 Months Ended					48 Months Ended		90 Months Ended
	Jan. 01, 2021	Jan. 01, 2020	Mar. 31, 2018 USD ($)	Feb. 28, 2018 USD ($)	Jan. 30, 2018 USD ($)	Jun. 09, 2017 USD ($)	Dec. 20, 2016 USD ($)	Jan. 01, 2016	Feb. 20, 2014 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2009 USD ($) utility MW	Dec. 31, 2008	Dec. 31, 2022 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2016 USD ($)	Sep. 28, 2017 USD ($)	Dec. 31, 2013
Loss Contingencies [Line Items]
Construction work in progress			$ 7,460							$ 7,460			$ 6,904
GEORGIA POWER CO
Loss Contingencies [Line Items]
Number of construction units approved | utility														2
Electric generating capacity in mega watts under consortium agreement | MW														1,100
Percentage of proportionate share owed in consortium agreement															45.70%
Construction work in progress			4,800							4,800			4,613
Estimated in-service capital cost														$ 4,418
Financing costs collected, net of tax										1,600
Additional construction capital costs							$ 3,300
Retail rate of return on common equity																				10.95%
Eligible project costs to be reimbursed									$ 3,460
Plant Vogtle Units 3 And 4 | GEORGIA POWER CO
Loss Contingencies [Line Items]
Cost settlement agreement revised forecast			8,800							8,800
Cost settlement agreement revised forecast, net of payments			7,300							7,300
Guarantor obligations						$ 1,700
Customer refund					$ 188
Construction work in progress			3,600							$ 3,600
Construction financing costs			$ 1,600
Percentage of ownership interest required for voting for continuing construction			90.00%							90.00%
Public utilities, increase in construction budget										$ 1,000
Extension in project schedule										1 year
Percentage of approval required to change primary construction contractor			90.00%							90.00%
Percentage of approval required for material amendments			67.00%							67.00%
Increase (decrease) in tariff					$ 50
Additional construction capital costs				$ 448														$ 4,400
Public utilities, approved return on equity percentage								10.00%
Return on equity reduction, negative impact on earnings													$ 25
Requested rate increase (decrease) amount										$ (500)
Scenario, Forecast | GEORGIA POWER CO
Loss Contingencies [Line Items]
Amendment to estimated in-service capital cost																	$ 5,680
Scenario, Forecast | Plant Vogtle Units 3 And 4 | GEORGIA POWER CO
Loss Contingencies [Line Items]
Construction financing costs											$ 3,100
Public utilities, approved return on equity percentage	5.30%	8.30%
Return on equity reduction, negative impact on earnings												$ 100				$ 585
Vogtle Owners | Plant Vogtle Units 3 And 4 | GEORGIA POWER CO
Loss Contingencies [Line Items]
Period of notice required in the event letters of credit are not renewed						30 days
FFB Loan | GEORGIA POWER CO
Loss Contingencies [Line Items]
Long-term line of credit			$ 2,600							$ 2,600
Conditional borrowing commitment																			$ 1,670