Fair Value Measurements - Schedule of Financial Instruments for which Carrying Amount did not Equal Fair Value (Details) $ in Billions |
Jun. 30, 2026
USD ($)
|
|---|---|
| Long-term debt, including securities due within one year: | |
| Carrying amount | $ 72.7 |
| Fair value | 68.0 |
| ALABAMA POWER CO | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 12.0 |
| Fair value | 10.7 |
| GEORGIA POWER CO | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 22.3 |
| Fair value | 20.7 |
| MISSISSIPPI POWER CO | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 1.8 |
| Fair value | 1.7 |
| SOUTHERN POWER CO | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 3.0 |
| Fair value | 2.9 |
| SOUTHERN Co GAS | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 9.3 |
| Fair value | $ 8.4 |