REGULATORY MATTERS - APC Rate CNP New Plant (Details) - Alabama Power - USD ($) $ in Millions	Mar. 24, 2023	Dec. 01, 2023	Oct. 03, 2022
Public Utilities, General Disclosures [Line Items]
Increase to annual revenue requirement		$ 91	$ 34
Increase to annual revenue requirement, percentage		1.40%	0.60%
Requested rate increase (decrease), amount	$ 78
Requested rate increase (decrease), percentage	1.10%