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	Jul. 31, 2024	Jun. 30, 2023	Jul. 31, 2022	Jun. 30, 2022	Feb. 28, 2022	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2021	Oct. 31, 2024	Oct. 31, 2023
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount		$ (5)	$ (7)		$ 18					$ 9
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	$ 18					$ 43
Over (under) recovered fuel cost								$ (32)	$ (50)		$ (25)	$ (61)
Retail ECM
Public Utilities, General Disclosures [Line Items]
Over (under) recovered fuel cost								32	27
MRA Revenue
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount								4	22
Over (under) recovered fuel cost								$ 19	$ (5)
MRA Revenue \| Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount							$ (19)