FAIR VALUE MEASUREMENTS - Financial Instruments for which Carrying Amount did not Equal Fair Value (Details) $ in Millions |
Jun. 30, 2020
USD ($)
|
|---|---|
| Long-term debt, including securities due within one year: | |
| Carrying amount | $ 46,513 |
| Fair value | 53,079 |
| ALABAMA POWER CO | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 8,519 |
| Fair value | 10,008 |
| GEORGIA POWER CO | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 12,720 |
| Fair value | 15,092 |
| MISSISSIPPI POWER CO | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 1,404 |
| Fair value | 1,571 |
| SOUTHERN POWER CO | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 4,097 |
| Fair value | 4,423 |
| SOUTHERN Co GAS | |
| Long-term debt, including securities due within one year: | |
| Carrying amount | 5,827 |
| Fair value | $ 6,817 |