REGULATORY MATTERS - APC Certificate of Convenience and Necessity and RGC (Details) $ in Millions		12 Months Ended
	Jul. 12, 2022 MW	Dec. 31, 2020 USD ($) MW	Dec. 31, 2022 USD ($) MW	Dec. 31, 2021 USD ($)	Dec. 31, 2019 MW
Schedule of Regulatory Assets and Liabilities [Line Items]
Construction work in progress			$ 10,896	$ 8,771
Plant in service, net of depreciation			82,232	81,513
Alabama Power
Schedule of Regulatory Assets and Liabilities [Line Items]
Approved additional generating capacity, demand-side management and distributed energy resource programs | MW		200
Additional generating capacity, petitioned megawatts, total | MW					2,400
Construction work in progress			1,526	1,147
Plant in service, net of depreciation			$ 23,002	$ 22,822
Renewable generation certificate, authorized generating capacity (in MWs) | MW			500
Renewable generation certificate, generating capacity (in MWs) | MW			330
Alabama Power | Calhoun Power Company, LLC
Schedule of Regulatory Assets and Liabilities [Line Items]
Approximate nameplate capacity (in MWs) | MW	743
Alabama Power | Year 2020
Schedule of Regulatory Assets and Liabilities [Line Items]
PPA, additional generating capacity (in MWs) | MW		240
Plant Barry Unit 8 | Alabama Power
Schedule of Regulatory Assets and Liabilities [Line Items]
Approximate nameplate capacity (in MWs) | MW		720
Costs incurred, percentage of estimated in-service cost		5.00%
Estimated in-service cost		$ 652
Construction work in progress			$ 518
Construction in progress, work in progress amount			513
Plant in service, net of depreciation			$ 5