REGULATORY MATTERS - GPC Rate Plans and COVID-19 Costs (Details) - Georgia Power - USD ($) $ in Millions		12 Months Ended
	Sep. 17, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2013	Oct. 31, 2020	Jun. 30, 2020
Public Utilities, General Disclosures [Line Items]
Retail rate of return on common equity	10.50%				10.95%
Portion of actual earnings above approved ROE band applied to reduce regulatory assets (percent)	40.00%
Portion of actual earnings above approved ROE band retained by subsidiary company	20.00%
Portion of actual earnings above approved ROE band refunded to customers	40.00%	50.00%	50.00%		66.67%
Portion of actual earnings above approved ROE band retained by Georgia Power					33.33%
Portion of actual earnings above approved ROE band refunded to customers, used to reduce regulatory assets		50.00%		50.00%
Portion of actual earning above approved ROE band refunded to customers, used to reduce regulatory assets, value		$ 60		$ 50
Portion of actual earnings above approved ROE band refunded to customers, value		50	$ 60			$ 60	$ 50
Customer refund liability in absence of base rate case			110
Incremental COVID-19 costs deferred		$ 38
Customer Refunds
Public Utilities, General Disclosures [Line Items]
Portion of actual earnings above approved ROE band refunded to customers, value			$ 110
Maximum
Public Utilities, General Disclosures [Line Items]
Regulatory asset amortization period		32 years
Retail rate of return on common equity	12.00%				12.00%
Maximum | Remaining Net Book Value of Retired Assets
Public Utilities, General Disclosures [Line Items]
Regulatory asset amortization period			3 years
Minimum
Public Utilities, General Disclosures [Line Items]
Retail rate of return on common equity	9.50%				10.00%