RETIREMENT BENEFITS - Accumulated Benefit Obligation (Details) - Pension plans - USD ($) $ in Millions |
Dec. 31, 2024 |
Dec. 31, 2023 |
|---|---|---|
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total accumulated benefit obligation for the pension plans | $ 11,437 | $ 11,991 |
| Alabama Power | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total accumulated benefit obligation for the pension plans | 2,617 | 2,746 |
| Georgia Power | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total accumulated benefit obligation for the pension plans | 3,438 | 3,674 |
| Mississippi Power | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total accumulated benefit obligation for the pension plans | 519 | 546 |
| Southern Power | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total accumulated benefit obligation for the pension plans | 140 | 145 |
| Southern Company Gas | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total accumulated benefit obligation for the pension plans | $ 779 | $ 808 |