REGULATORY MATTERS - MPC Environmental Compliance Overview Plan (Details) - Mississippi Power - USD ($) $ in Millions		1 Months Ended						12 Months Ended
	Feb. 12, 2024	Jun. 30, 2023	Apr. 30, 2023	Jun. 30, 2022	Apr. 30, 2022	Jun. 30, 2021	May 31, 2021	Dec. 31, 2021
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount		$ (7)		$ 18		$ 16	$ 28	$ 9
Environmental Compliance Overview Plan
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount			$ 3		$ 1	$ (9)
Environmental Compliance Overview Plan | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount	$ 9