INCOME TAXES - Federal ITC/PTC Carryforwards (Details) - ITC and PTC carryforwards $ in Millions	Dec. 31, 2023 USD ($)
Operating Loss Carryforwards [Line Items]
Federal ITC/PTC carryforwards	$ 829
Alabama Power
Operating Loss Carryforwards [Line Items]
Federal ITC/PTC carryforwards	12
Georgia Power
Operating Loss Carryforwards [Line Items]
Federal ITC/PTC carryforwards	131
Southern Power
Operating Loss Carryforwards [Line Items]
Federal ITC/PTC carryforwards	$ 481