DERIVATIVES - Interest Rate Derivatives (Details) - Interest rate derivatives $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Derivative [Line Items]
Notional Amount	$ 2,200
Fair Value Gain (Loss) December 31, 2023	(264)
Southern Company | Fair Value Hedges of Existing Debt | Date one
Derivative [Line Items]
Notional Amount	$ 400
Weighted Average Interest Rate Paid	0.80%
Interest Rate Received	1.75%
Fair Value Gain (Loss) December 31, 2023	$ (46)
Southern Company | Fair Value Hedges of Existing Debt | Date 2
Derivative [Line Items]
Notional Amount	$ 1,000
Weighted Average Interest Rate Paid	2.48%
Interest Rate Received	3.70%
Fair Value Gain (Loss) December 31, 2023	$ (139)
Southern Company Gas | Fair Value Hedges of Existing Debt
Derivative [Line Items]
Notional Amount	$ 500
Weighted Average Interest Rate Paid	0.49%
Interest Rate Received	1.75%
Fair Value Gain (Loss) December 31, 2023	$ (79)
Georgia Power | Cash Flow Hedges of Forecasted Debt
Derivative [Line Items]
Notional Amount	$ 150
Weighted Average Interest Rate Paid	4.01%
Fair Value Gain (Loss) December 31, 2023	$ 0
Mississippi Power | Cash Flow Hedges of Forecasted Debt | Date one
Derivative [Line Items]
Notional Amount	$ 75
Weighted Average Interest Rate Paid	3.84%
Fair Value Gain (Loss) December 31, 2023	$ 0
Mississippi Power | Cash Flow Hedges of Forecasted Debt | Date 2
Derivative [Line Items]
Notional Amount	$ 75
Weighted Average Interest Rate Paid	4.04%
Fair Value Gain (Loss) December 31, 2023	$ 0