Derivatives - Schedule of Energy-Related Derivatives (Details) - Energy-related, Natural Gas MMBTU in Millions	Sep. 30, 2024 MMBTU
Energy-related derivative contracts
Net Purchased mmBtu	479.0
ALABAMA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	130.0
GEORGIA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	127.0
MISSISSIPPI POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	109.0
SOUTHERN POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	6.0
SOUTHERN Co GAS
Energy-related derivative contracts
Net Purchased mmBtu	107.0
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	118.0
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	11.0