Derivatives - Schedule of Energy-Related Derivatives (Details) - Energy-related, Natural Gas MMBTU in Millions	Sep. 30, 2022 MMBTU
Energy-related derivative contracts
Net Purchased mmBtu	399.0
ALABAMA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	105.0
GEORGIA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	116.0
MISSISSIPPI POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	82.0
SOUTHERN POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	11.0
SOUTHERN Co GAS
Energy-related derivative contracts
Net Purchased mmBtu	85.0
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	95.7
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	10.6