Derivatives - Schedule of Interest Rate Derivatives (Details) - Interest rate derivatives $ in Millions	6 Months Ended
	Jun. 30, 2023 USD ($)
Derivative [Line Items]
Notional Amount	$ 2,150
Fair Value Gain (Loss)	(300)
Southern Company parent(a) | Fair Value Hedges of Existing Debt | March 2028
Derivative [Line Items]
Notional Amount	$ 400
Interest Rate Received	1.75%
Fair Value Gain (Loss)	$ (56)
Southern Company parent(a) | Fair Value Hedges of Existing Debt | April 2030
Derivative [Line Items]
Notional Amount	$ 1,000
Interest Rate Received	3.70%
Fair Value Gain (Loss)	$ (160)
SOUTHERN Co GAS | Cash Flow Hedges of Forecasted Debt
Derivative [Line Items]
Notional Amount	$ 250
Weighted Average Interest Rate Paid	3.40%
Fair Value Gain (Loss)	$ 4
SOUTHERN Co GAS | Fair Value Hedges of Existing Debt
Derivative [Line Items]
Notional Amount	$ 500
Interest Rate Received	1.75%
Fair Value Gain (Loss)	$ (88)
LIBOR | Southern Company parent(a) | Fair Value Hedges of Existing Debt | March 2028
Derivative [Line Items]
Weighted Average Interest Rate Paid	0.68%
LIBOR | Southern Company parent(a) | Fair Value Hedges of Existing Debt | April 2030
Derivative [Line Items]
Weighted Average Interest Rate Paid	2.36%
LIBOR | SOUTHERN Co GAS | Fair Value Hedges of Existing Debt
Derivative [Line Items]
Weighted Average Interest Rate Paid	0.38%