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RETIREMENT BENEFITS - Accumulated Benefit Obligation (Details) - Pension plans - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
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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

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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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