REGULATORY MATTERS - APC Rate ERC (Details) - Alabama Power $ in Millions	1 Months Ended				12 Months Ended
	Jan. 31, 2023 $ / KWH_Kilowatt_hour	Dec. 31, 2020 USD ($) $ / KWH_Kilowatt_hour	Oct. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) $ / KWH_Kilowatt_hour	Dec. 31, 2021 USD ($) $ / KWH_Kilowatt_hour	Dec. 31, 2018 $ / KWH_Kilowatt_hour
Schedule of Regulatory Assets and Liabilities [Line Items]
Current billing rates under rate ECR (usd per KWH) | $ / KWH_Kilowatt_hour		1.960		0.02160	0.05910	0.02353
Current billing rates under rate ECR, percentage decrease		1.84%		1.82%
Current billing rates under rate ECR, decrease, amount		$ 103		$ 102
Reduction of over-collected fuel balance			$ 94
Over (under) recovered fuel cost		$ 18			$ (126)
Rate RSE refund liability, portion attributable to reduce under recovered balance					$ 126
Scenario, Forecast
Schedule of Regulatory Assets and Liabilities [Line Items]
Current billing rates under rate ECR (usd per KWH) | $ / KWH_Kilowatt_hour	0.05910