Derivatives - Schedule of Energy-Related Derivatives (Details) - Energy-related, Natural Gas MMBTU in Millions	Mar. 31, 2024 MMBTU
Energy-related derivative contracts
Net Purchased mmBtu	475.0
ALABAMA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	125.0
GEORGIA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	142.0
MISSISSIPPI POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	108.0
SOUTHERN POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	7.0
SOUTHERN Co GAS
Energy-related derivative contracts
Net Purchased mmBtu	93.0
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	100.7
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	7.8