REGULATORY MATTERS - Nuclear Construction (Details) - Georgia Power $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2009 utility MW	Jun. 30, 2018 USD ($)
Loss Contingencies [Line Items]
Number of construction units approved | utility			2
Electric generating capacity (mw) | MW			1,100
Plant Vogtle Units 3 And 4
Loss Contingencies [Line Items]
Percent ownership		45.70%
Construction contingency estimate, subject to rate recovery evaluation		$ 140		$ 366
Construction financing costs		2,200
Additional base capital costs per month		50
AFUDC per month		$ 12
Plant Vogtle Units 3 And 4 | Scenario, Forecast
Loss Contingencies [Line Items]
Construction financing costs	$ 3,100
Vogtle Owners | Plant Vogtle Units 3 And 4
Loss Contingencies [Line Items]
Period of notice required in the event letters of credit are not renewed		30 days