RETIREMENT BENEFITS - 401K Plan Matching Contributions (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2024 |
Dec. 31, 2023 |
Dec. 31, 2022 |
|
| Defined Benefit Plan Disclosure [Line Items] | |||
| Defined contribution plan, cost | $ 137 | $ 131 | $ 124 |
| Alabama Power | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Defined contribution plan, cost | 29 | 28 | 26 |
| Georgia Power | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Defined contribution plan, cost | 31 | 31 | 29 |
| Mississippi Power | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Defined contribution plan, cost | 5 | 5 | 5 |
| Southern Power | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Defined contribution plan, cost | 3 | 3 | 3 |
| Southern Company Gas | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Defined contribution plan, cost | $ 20 | $ 18 | $ 17 |