Derivatives - Schedule of Energy-Related Derivatives (Details) - Energy-related, Natural Gas MMBTU in Millions	Jun. 30, 2026 MMBTU
Energy-related derivative contracts
Net Purchased mmBtu	469
ALABAMA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	155
GEORGIA POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	117
MISSISSIPPI POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	114
SOUTHERN POWER CO
Energy-related derivative contracts
Net Purchased mmBtu	8
SOUTHERN Co GAS
Energy-related derivative contracts
Net Purchased mmBtu	75
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	85
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