REGULATORY MATTERS - APC Rate CNP (Details) - Alabama Power - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Schedule of Regulatory Assets and Liabilities [Line Items]
Under recovered certified power purchase agreements		$ 84	$ 103
Retail revenue requirement for environmental compliance		50	$ 23	$ 255
Retail revenue requirement for environmental compliance, as a percentage			(0.30%)	3.70%
Over (under) recovered environmental clause		(35)	$ (33)
Public utilities, approved rate increase (decrease), amount	$ 318
Approved rate increase, percent	4.60%
Other regulatory assets, current
Schedule of Regulatory Assets and Liabilities [Line Items]
Under recovered certified power purchase agreements		17	18
Over (under) recovered environmental clause			(8)
Other regulatory assets, deferred
Schedule of Regulatory Assets and Liabilities [Line Items]
Under recovered certified power purchase agreements		$ 67	85
Over (under) recovered environmental clause			$ (25)