Derivatives - Schedule of Energy-Related Derivatives (Details) - Energy-related, Natural Gas MMBTU in Millions	Sep. 30, 2023 MMBTU
Energy-related derivative contracts
Net Purchased mmBtu	422.0
ALABAMA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	109.0
GEORGIA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	104.0
MISSISSIPPI POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	80.0
SOUTHERN POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	8.0
SOUTHERN Co GAS
Energy-related derivative contracts
Net Purchased mmBtu	121.0
SOUTHERN Co GAS | Energy-related derivatives not designated as hedging instruments | Long
Energy-related derivative contracts
Derivative nonmonetary notional amount net long short position volume	135.5
SOUTHERN Co GAS | Energy-related derivatives not designated as hedging instruments | Short
Energy-related derivative contracts
Derivative nonmonetary notional amount net long short position volume	14.2