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RETIREMENT BENEFITS - Amounts Recognized in Balance Sheets and Amounts in AOCI (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | $ 7,037 | $ 6,264 |
Other current liabilities | (1,100) | (1,029) |
Employee benefit obligations | (1,011) | (1,115) |
Other regulatory liabilities, deferred | (692) | (715) |
Regulatory asset |  | 66 | $ 216
Other deferred charges and assets | 1,467 | 1,468 |
Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Prepaid pension costs | 2,674 | 2,079 |
Other regulatory assets, deferred | 2,708 | 2,960 |
Other current liabilities | (68) | (64) |
Employee benefit obligations | (611) | (649) |
Other regulatory liabilities, deferred | (50) | (47) |
AOCI | 52 | 79 |
Other Postretirement Benefits Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 24 | 23 |
Other current liabilities | (6) | (6) |
Employee benefit obligations | (212) | (285) |
Other regulatory liabilities, deferred | (213) | (231) |
AOCI | (14) | (9) |
Prepaid pension and other postretirement benefit costs | 0 | 0 |
Alabama Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 1,815 | 1,858 |
Other current liabilities | (219) | (191) |
Employee benefit obligations | (148) | (155) |
Other regulatory liabilities, deferred | (271) | (291) |
Regulatory asset | 70 | 76 | 97
Prepaid pension and other postretirement benefit costs | 841 | 659 |
Other deferred charges and assets | 391 | 414 |
Alabama Power | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Prepaid pension costs | 746 | 585 |
Other regulatory assets, deferred | 741 | 821 |
Other current liabilities | (13) | (11) |
Employee benefit obligations | (102) | (106) |
Other regulatory liabilities, deferred | 0 | 0 |
AOCI | 0 | 0 |
Alabama Power | Other Postretirement Benefits Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 0 | 0 |
Other current liabilities | 0 | 0 |
Employee benefit obligations | 0 | 0 |
Other regulatory liabilities, deferred | (45) | (48) |
AOCI | 0 | 0 |
Prepaid pension and other postretirement benefit costs | 95 | 74 |
Georgia Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 3,814 | 2,890 |
Other current liabilities | (296) | (365) |
Employee benefit obligations | (205) | (248) |
Regulatory asset |  |  | 83
Other deferred charges and assets | 615 | 508 |
Georgia Power | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Prepaid pension costs | 897 | 706 |
Other regulatory assets, deferred | 973 | 1,051 |
Other current liabilities | (13) | (13) |
Employee benefit obligations | (98) | (131) |
Other regulatory liabilities, deferred | 0 | 0 |
AOCI | 0 | 0 |
Georgia Power | Other Postretirement Benefits Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 3 | 11 |
Other current liabilities | 0 | 0 |
Employee benefit obligations | (68) | (79) |
Other regulatory liabilities, deferred | (67) | (85) |
AOCI | 0 | 0 |
Prepaid pension and other postretirement benefit costs | 0 | 0 |
Mississippi Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 259 | 285 |
Other current liabilities | (95) | (90) |
Employee benefit obligations | (65) | (67) |
Other regulatory liabilities, deferred | (121) | (92) |
Regulatory asset | 52 | 44 | $ 36
Other deferred charges and assets | 74 | 85 |
Mississippi Power | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Prepaid pension costs | 124 | 99 |
Other regulatory assets, deferred | 144 | 152 |
Other current liabilities | (2) | (2) |
Employee benefit obligations | (25) | (27) |
Other regulatory liabilities, deferred | 0 | 0 |
AOCI | 0 | 0 |
Mississippi Power | Other Postretirement Benefits Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 0 | 0 |
Other current liabilities | 0 | 0 |
Employee benefit obligations | (31) | (32) |
Other regulatory liabilities, deferred | (9) | (10) |
AOCI | 0 | 0 |
Prepaid pension and other postretirement benefit costs | 0 | 0 |
Southern Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other current liabilities | (96) | (97) |
Other deferred charges and assets | 232 | 262 |
Southern Power | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Prepaid pension costs | 41 | 31 |
Other regulatory assets, deferred | 0 | 0 |
Other current liabilities | (2) | (2) |
Employee benefit obligations | (18) | (21) |
Other regulatory liabilities, deferred | 0 | 0 |
AOCI | 11 | 20 |
Southern Power | Other Postretirement Benefits Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 0 | 0 |
Other current liabilities | (1) | (1) |
Employee benefit obligations | (8) | (8) |
Other regulatory liabilities, deferred | 0 | 0 |
AOCI | 0 | 1 |
Prepaid pension and other postretirement benefit costs | 0 | 0 |
Southern Company Gas |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 481 | 504 |
Other current liabilities | (237) | (232) |
Employee benefit obligations | (78) | (110) |
Other deferred charges and assets | 192 | 181 |
Southern Company Gas | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Prepaid pension costs | 191 | 158 |
Other regulatory assets, deferred | 126 | 143 |
Other current liabilities | (4) | (3) |
Employee benefit obligations | (51) | (58) |
Other regulatory liabilities, deferred | 0 | 0 |
AOCI | (54) | (45) |
Regulatory asset | 155 | 173 |
Southern Company Gas | Other Postretirement Benefits Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Other regulatory assets, deferred | 0 | 0 |
Other current liabilities | 0 | 0 |
Employee benefit obligations | (15) | (44) |
Other regulatory liabilities, deferred | (84) | (68) |
AOCI | (15) | (10) |
Regulatory asset | 16 | 24 |
Prepaid pension and other postretirement benefit costs | $ 0 | $ 0 |

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