REGULATORY MATTERS - GPC Nuclear Construction (Details) $ in Millions			1 Months Ended	12 Months Ended
	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Apr. 30, 2020	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2012 utility MW	Jun. 30, 2018 USD ($)
Public Utilities, General Disclosures [Line Items]
Estimated loss on Plant Vogtle Units 3 and 4				$ 325	$ 0	$ 1,060
Georgia Power
Public Utilities, General Disclosures [Line Items]
Number of construction units approved | utility							2
Electric generating capacity (in MWs) | MW							1,100
Estimated loss on Plant Vogtle Units 3 and 4				$ 325	$ 0	$ 1,060
Plant Vogtle Units 3 And 4 | Georgia Power
Public Utilities, General Disclosures [Line Items]
Percent ownership	45.70%			45.70%
Estimated construction financing costs	$ 3,000			$ 3,000
Construction financing costs incurred to date	2,600			2,600
Construction contingency estimate, subject to rate recovery evaluation		$ 366
Estimated cost to complete, amount in excess of initial construction contingency estimate	171			171				$ 34
Estimated cost to complete, additional construction contingency estimate	5			$ 5				$ 115
Estimated loss on Plant Vogtle Units 3 and 4, net of tax	131	111
Estimated loss on Plant Vogtle Units 3 and 4	176	$ 149
Expected number of positions reduced, percent			20.00%
Plant Vogtle Units 3 And 4 | Georgia Power | Minimum | COVID-19
Public Utilities, General Disclosures [Line Items]
Estimated months of productivity loss				3 months
Construction financing costs	150			$ 150
Plant Vogtle Units 3 And 4 | Georgia Power | Maximum | COVID-19
Public Utilities, General Disclosures [Line Items]
Estimated months of productivity loss				4 months
Construction financing costs	$ 190			$ 190
Plant Vogtle Units 3 And 4 | Georgia Power | Vogtle Owners
Public Utilities, General Disclosures [Line Items]
Period of notice required in the event letters of credit are not renewed				30 days