REGULATORY MATTERS - MPC System Restoration Rider and Department of Revenue Audit (Details) - USD ($)	1 Months Ended				12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2021	May 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Feb. 01, 2024	Apr. 04, 2023	Apr. 03, 2023
Public Utilities, General Disclosures [Line Items]
Reliability reserve, amount deferred					$ 63,000,000	$ 191,000,000
Total deferred charges and other assets					19,069,000,000	20,148,000,000
Regulatory asset					66,000,000	216,000,000
Major storms
Public Utilities, General Disclosures [Line Items]
Storm damage reserves accrual						239,000,000	$ 286,000,000
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	$ (7,000,000)	$ 18,000,000	$ 16,000,000	$ 28,000,000			9,000,000
Reliability reserve, amount deferred					11,000,000	25,000,000			$ 11,700,000	$ 8,300,000
Reliability reserve					36,000,000	25,000,000
Total deferred charges and other assets					887,000,000	828,000,000
Regulatory asset					44,000,000	36,000,000
Mississippi Power | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Reliability reserve, amount deferred								$ 12,600,000
Mississippi Power | Retail electric revenues
Public Utilities, General Disclosures [Line Items]
Property damage reserve					45,000,000	37,000,000
Mississippi Power | Major storms
Public Utilities, General Disclosures [Line Items]
Storm damage reserves accrual					$ 11,700,000	$ 6,900,000	$ (1,800,000)