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RETIREMENT BENEFITS - Projected Benefit Plan Obligations (Details) - Pension plans - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
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Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | $ 12,564 | $ 13,252 | $ 12,602
Alabama Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 2,908 | 3,076 | 2,906
Georgia Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 3,733 | 4,009 | 3,851
Mississippi Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 567 | 599 | 569
SOUTHERN POWER CO |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 167 | 177 | 163
Southern Company Gas |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 842 | $ 882 | $ 868
Qualified pension plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 11,886 |  |
Qualified pension plan | Alabama Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 2,794 |  |
Qualified pension plan | Georgia Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 3,622 |  |
Qualified pension plan | Mississippi Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 540 |  |
Qualified pension plan | SOUTHERN POWER CO |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 146 |  |
Qualified pension plan | Southern Company Gas |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 788 |  |
Non-qualified pension plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 678 |  |
Non-qualified pension plan | Alabama Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 114 |  |
Non-qualified pension plan | Georgia Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 111 |  |
Non-qualified pension plan | Mississippi Power |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 27 |  |
Non-qualified pension plan | SOUTHERN POWER CO |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | 21 |  |
Non-qualified pension plan | Southern Company Gas |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligations: | $ 54 |  |

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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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