ASSET RETIREMENT OBLIGATIONS - Accumulated Provisions for the External Decommissioning Trust Funds (Details) - External decommissioning trust funds - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Georgia Power
Public Utilities, General Disclosures [Line Items]
Accumulated provisions for decommissioning	$ 1,217	$ 1,145
Plant Farley | Alabama Power
Public Utilities, General Disclosures [Line Items]
Accumulated provisions for decommissioning	1,324	1,156
Plant Hatch | Georgia Power
Public Utilities, General Disclosures [Line Items]
Accumulated provisions for decommissioning	757	716
Plant Vogtle Units 1 and 2 | Georgia Power
Public Utilities, General Disclosures [Line Items]
Accumulated provisions for decommissioning	$ 460	$ 429