CONTINGENCIES - Other Matters (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended		36 Months Ended	60 Months Ended
	Feb. 20, 2020	Dec. 31, 2018	Dec. 31, 2024	Dec. 31, 2020	Dec. 31, 2023	Jan. 15, 2024	Mar. 31, 2020
MISSISSIPPI POWER CO | Kemper IGCC
Loss Contingencies [Line Items]
Government grants received		$ 387
MISSISSIPPI POWER CO | Scenario, Forecast | Kemper IGCC
Loss Contingencies [Line Items]
Asset retirement obligation, expected cost				$ 10
Liabilities incurred			$ 5	$ 17
GULF POWER CO | Scenario, Forecast | Plant Daniel Units 1 And 2
Loss Contingencies [Line Items]
Undivided ownership interest to be sold						50.00%
Undivided ownership interest, ownership interest in individual unit						100.00%
Minimum | MISSISSIPPI POWER CO | Scenario, Forecast | Kemper IGCC
Loss Contingencies [Line Items]
Liabilities incurred					$ 15
Maximum | MISSISSIPPI POWER CO | Scenario, Forecast | Kemper IGCC
Loss Contingencies [Line Items]
Liabilities incurred					$ 17
PennEast Pipelines
Loss Contingencies [Line Items]
Construction contingency, extension request, term	2 years
PennEast Pipelines | SOUTHERN Co GAS
Loss Contingencies [Line Items]
Construction contingency estimate							$ 300