Regulatory Matters - GPC Nuclear Construction (Details) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2012 utility MW	Aug. 31, 2018
Loss Contingencies [Line Items]
Estimated loss on Plant Vogtle Units 3 and 4	$ 460		$ 149	$ 508	$ 149
GEORGIA POWER CO
Loss Contingencies [Line Items]
Estimated loss on Plant Vogtle Units 3 and 4	460	$ 48	149	508	149
Estimated loss on Plant Vogtle Units 3 and 4, net of tax	$ 343	36	$ 111	$ 379	$ 111
GEORGIA POWER CO | Plant Vogtle Units 3 And 4
Loss Contingencies [Line Items]
Proportionate ownership share	45.70%			45.70%
Number of construction units approved | utility						2
Electric generating capacity in mega watts under consortium agreement | MW						1,100
Estimated cost to complete, construction contingency estimate, financing costs	$ 3,200			$ 3,200
Estimated cost to complete, construction contingency estimate, financing costs, incurred to date	2,700			2,700
Construction contingency estimate	341	84		341
Construction contingency estimate, additional amount	119	$ 48		119
Base project capital cost forecast, monthly				25
Monthly AFUDC				$ 15
Percentage of ownership interest required for voting for continuing construction							90.00%
GEORGIA POWER CO | Plant Vogtle Units 3 And 4 | Vogtle Owners
Loss Contingencies [Line Items]
Period of notice required in the event letters of credit are not renewed				30 days
Minimum | GEORGIA POWER CO | Plant Vogtle Units 3 And 4 | COVID-19
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss, loss of productivity, term				3 months
Estimate of possible loss	160			$ 160
Maximum | GEORGIA POWER CO | Plant Vogtle Units 3 And 4 | COVID-19
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss, loss of productivity, term				4 months
Estimate of possible loss	$ 200			$ 200