REGULATORY MATTERS - MPC Fuel Cost Recovery and Ad Valorem Tax Adjustment (Details) - Mississippi Power - USD ($) $ in Millions		1 Months Ended											12 Months Ended
	Feb. 06, 2024	Jan. 31, 2024	Jun. 30, 2023	Jan. 31, 2023	Nov. 30, 2022	Jul. 31, 2022	Jun. 30, 2022	Feb. 28, 2022	Jan. 31, 2022	Jun. 30, 2021	May 31, 2021	Feb. 28, 2021	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2022
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount			$ (7)				$ 18			$ 16	$ 28		$ 9
Public utilities, valorem taxes previously recovered, amount											$ 19
Ad Valorem Tax Adjustment
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount						$ 5
Retail electric revenues
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount			$ 25		$ 25			$ 43				$ 2
Over (under) recovered fuel cost														$ (50)	$ (1)
Retail electric revenues | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount	$ 18
Over (under) recovered fuel cost	$ (61)
MRA Revenue
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount				$ 22					$ 11
Over (under) recovered fuel cost														5	$ (6)
MRA Revenue | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount		$ (4)
Retail ECM
Public Utilities, General Disclosures [Line Items]
Over (under) recovered fuel cost														$ 27