REGULATORY MATTERS - MPC System Restoration Rider (Details) - USD ($)			1 Months Ended				12 Months Ended
	Feb. 14, 2023	Feb. 13, 2023	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	May 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Public Utilities, General Disclosures [Line Items]
Reliability reserve, amount deferred							$ 191,000,000
Subsequent Event
Public Utilities, General Disclosures [Line Items]
Minimum annual accrual, amount		$ 8,000,000
Major storms
Public Utilities, General Disclosures [Line Items]
Storm damage reserves accrual							239,000,000	$ 286,000,000	$ 326,000,000
Mississippi Power
Public Utilities, General Disclosures [Line Items]
Threshold above which actual damages are charged to the reserve (individually exceed)							50,000
Public utilities, approved rate increase (decrease), amount			$ 18,000,000	$ 9,000,000	$ 16,000,000	$ 28,000,000			(16,700,000)
Target property damage reserve				75,000,000				75,000,000
Reliability reserve, amount deferred							25,000,000
Mississippi Power | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount	$ 12,000,000
Mississippi Power | Retail electric revenues
Public Utilities, General Disclosures [Line Items]
Property damage reserve				$ 31,000,000			37,000,000	31,000,000
Mississippi Power | Major storms
Public Utilities, General Disclosures [Line Items]
Storm damage reserves accrual							$ 6,900,000	$ (1,800,000)	$ 800,000