REGULATORY MATTERS - APC Rate CNP (Details) - Alabama Power - USD ($) $ in Millions		12 Months Ended
	Dec. 06, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Regulatory Assets and Liabilities [Line Items]
Under recovered certified power purchase agreements		$ 120	$ 84
Retail revenue requirement for environmental compliance		$ 255	59	$ 59
Retail revenue requirement for environmental compliance, as a percentage		3.70%
Over (under) recovered environmental clause		$ (47)	$ 16
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		18
Other regulatory assets, deferred
Schedule of Regulatory Assets and Liabilities [Line Items]
Under recovered certified power purchase agreements		$ 102