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RETIREMENT BENEFITS - Actuarial Assumptions (Details) | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.07% | 5.25% | 3.09%
Expected long-term return on plan assets | 8.30% | 8.40% | 8.25%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Pension plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.94% | 5.13% | 2.55%
Pension plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.19% | 5.36% | 3.34%
Pension plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.76% | 5.07% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Other postretirement benefit plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 4.99% | 5.18% | 2.90%
Expected long-term return on plan assets | 7.67% | 7.67% | 7.21%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Other postretirement benefit plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.90% | 5.08% | 2.32%
Other postretirement benefit plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.16% | 5.34% | 3.26%
Other postretirement benefit plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.64% | 4.99% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Alabama Power | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.08% | 5.26% | 3.12%
Expected long-term return on plan assets | 8.30% | 8.40% | 8.25%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Alabama Power | Pension plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.94% | 5.14% | 2.58%
Alabama Power | Pension plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.20% | 5.38% | 3.36%
Alabama Power | Pension plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.78% | 5.08% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Alabama Power | Other postretirement benefit plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.01% | 5.20% | 2.95%
Expected long-term return on plan assets | 7.97% | 7.95% | 7.54%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Alabama Power | Other postretirement benefit plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.90% | 5.09% | 2.38%
Alabama Power | Other postretirement benefit plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.17% | 5.35% | 3.30%
Alabama Power | Other postretirement benefit plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.67% | 5.01% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Georgia Power | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.06% | 5.25% | 3.07%
Expected long-term return on plan assets | 8.30% | 8.40% | 8.25%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Georgia Power | Pension plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.94% | 5.12% | 2.51%
Georgia Power | Pension plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.21% | 5.38% | 3.37%
Georgia Power | Pension plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.75% | 5.06% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Georgia Power | Other postretirement benefit plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 4.98% | 5.17% | 2.87%
Expected long-term return on plan assets | 7.59% | 7.49% | 6.88%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Georgia Power | Other postretirement benefit plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.89% | 5.07% | 2.30%
Georgia Power | Other postretirement benefit plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.16% | 5.34% | 3.27%
Georgia Power | Other postretirement benefit plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.61% | 4.98% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Mississippi Power | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.06% | 5.25% | 3.07%
Expected long-term return on plan assets | 8.30% | 8.40% | 8.25%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Mississippi Power | Pension plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.93% | 5.12% | 2.54%
Mississippi Power | Pension plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.19% | 5.37% | 3.35%
Mississippi Power | Pension plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.76% | 5.06% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Mississippi Power | Other postretirement benefit plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 4.98% | 5.17% | 2.88%
Expected long-term return on plan assets | 7.43% | 7.43% | 7.22%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Mississippi Power | Other postretirement benefit plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.90% | 5.08% | 2.27%
Mississippi Power | Other postretirement benefit plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.16% | 5.33% | 3.26%
Mississippi Power | Other postretirement benefit plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.63% | 4.98% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Southern Power | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.14% | 5.31% | 3.21%
Expected long-term return on plan assets | 8.30% | 8.40% | 8.25%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Southern Power | Pension plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.01% | 5.19% | 2.79%
Southern Power | Pension plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.20% | 5.37% | 3.36%
Southern Power | Pension plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.84% | 5.14% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Southern Power | Other postretirement benefit plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.06% | 5.24% | 3.07%
Expected long-term return on plan assets | 0.00% | 0.00% | 0.00%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Southern Power | Other postretirement benefit plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.94% | 5.12% | 2.55%
Southern Power | Other postretirement benefit plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.14% | 5.33% | 3.25%
Southern Power | Other postretirement benefit plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.73% | 5.06% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Southern Company Gas | Pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.05% | 5.24% | 3.04%
Expected long-term return on plan assets | 8.30% | 8.40% | 8.25%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Southern Company Gas | Pension plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.93% | 5.12% | 2.53%
Southern Company Gas | Pension plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.13% | 5.31% | 3.21%
Southern Company Gas | Pension plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.73% | 5.05% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |
Southern Company Gas | Other postretirement benefit plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 4.98% | 5.16% | 2.82%
Expected long-term return on plan assets | 6.36% | 6.59% | 6.08%
Annual salary increase, net periodic costs | 4.60% | 4.80% | 4.80%
Southern Company Gas | Other postretirement benefit plans | Discount rate – interest costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 4.89% | 5.07% | 2.17%
Southern Company Gas | Other postretirement benefit plans | Discount rate – service costs |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate, net periodic benefit costs | 5.16% | 5.33% | 3.22%
Southern Company Gas | Other postretirement benefit plans | Employee benefit obligations |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate – benefit obligations | 5.62% | 4.98% |
Annual salary increase, benefit obligations | 4.60% | 4.60% |

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- Definition Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related 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 (k)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of 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 (k)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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