DERIVATIVES - Foreign Currency Derivatives (Details) € in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2023 EUR (€)	Dec. 31, 2022 USD ($)
Foreign currency derivatives | Cash Flow Hedges of Forecasted Debt
Derivative [Line Items]
Pay Notional	$ 2,040
Receive Notional | €		€ 1,750
Fair Value Gain (Loss) December 31, 2023	(122)
Southern Power
Derivative [Line Items]
Fair Value Gain (Loss) December 31, 2023	(12)		$ (31)
Southern Power | Foreign currency derivatives | Cash Flow Hedges of Forecasted Debt
Derivative [Line Items]
Pay Notional	$ 564
Pay Rate	3.78%
Receive Notional | €		500
Receive Rate	1.85%
Southern Power | Foreign currency derivatives | Date | Cash Flow Hedges of Forecasted Debt
Derivative [Line Items]
Fair Value Gain (Loss) December 31, 2023	$ (22)
Southern Company | Foreign currency derivatives | Cash Flow Hedges of Forecasted Debt
Derivative [Line Items]
Fair Value Gain (Loss) December 31, 2023	(100)
Southern Company | Foreign currency derivatives | Date | Fair Value Hedges of Existing Debt
Derivative [Line Items]
Pay Notional	$ 1,476
Pay Rate	3.39%
Receive Notional | €		€ 1,250
Receive Rate	1.88%