RETIREMENT BENEFITS - Actuarial Assumptions (Details)
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12 Months Ended |
Dec. 31, 2024 |
Dec. 31, 2023 |
Dec. 31, 2022 |
| Pension plans |
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| Defined Benefit Plan Disclosure [Line Items] |
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| 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 |
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| Defined Benefit Plan Disclosure [Line Items] |
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|
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| Discount rate, net periodic benefit costs |
4.94%
|
5.13%
|
2.55%
|
| Pension plans | Discount rate – service costs |
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| Defined Benefit Plan Disclosure [Line Items] |
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|
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| Discount rate, net periodic benefit costs |
5.19%
|
5.36%
|
3.34%
|
| Pension plans | Employee benefit obligations |
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| Defined Benefit Plan Disclosure [Line Items] |
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| Discount rate – benefit obligations |
5.76%
|
5.07%
|
|
| Annual salary increase, benefit obligations |
4.60%
|
4.60%
|
|
| Other postretirement benefit plans |
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| Defined Benefit Plan Disclosure [Line Items] |
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| 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 |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate, net periodic benefit costs |
4.90%
|
5.08%
|
2.32%
|
| Other postretirement benefit plans | Discount rate – service costs |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate, net periodic benefit costs |
5.16%
|
5.34%
|
3.26%
|
| Other postretirement benefit plans | Employee benefit obligations |
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|
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate – benefit obligations |
5.64%
|
4.99%
|
|
| Annual salary increase, benefit obligations |
4.60%
|
4.60%
|
|
| Alabama Power | Pension plans |
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| Defined Benefit Plan Disclosure [Line Items] |
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| 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 |
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| Defined Benefit Plan Disclosure [Line Items] |
|
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| Discount rate, net periodic benefit costs |
4.94%
|
5.14%
|
2.58%
|
| Alabama Power | Pension plans | Discount rate – service costs |
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| Defined Benefit Plan Disclosure [Line Items] |
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| Discount rate, net periodic benefit costs |
5.20%
|
5.38%
|
3.36%
|
| Alabama Power | Pension plans | Employee benefit obligations |
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| Defined Benefit Plan Disclosure [Line Items] |
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| Discount rate – benefit obligations |
5.78%
|
5.08%
|
|
| Annual salary increase, benefit obligations |
4.60%
|
4.60%
|
|
| Alabama Power | Other postretirement benefit plans |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| 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 |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate, net periodic benefit costs |
4.90%
|
5.09%
|
2.38%
|
| Alabama Power | Other postretirement benefit plans | Discount rate – service costs |
|
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate, net periodic benefit costs |
5.17%
|
5.35%
|
3.30%
|
| Alabama Power | Other postretirement benefit plans | Employee benefit obligations |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate – benefit obligations |
5.67%
|
5.01%
|
|
| Annual salary increase, benefit obligations |
4.60%
|
4.60%
|
|
| Georgia Power | Pension plans |
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| Defined Benefit Plan Disclosure [Line Items] |
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| 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 |
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| Defined Benefit Plan Disclosure [Line Items] |
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| Discount rate, net periodic benefit costs |
4.94%
|
5.12%
|
2.51%
|
| Georgia Power | Pension plans | Discount rate – service costs |
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| Defined Benefit Plan Disclosure [Line Items] |
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| Discount rate, net periodic benefit costs |
5.21%
|
5.38%
|
3.37%
|
| Georgia Power | Pension plans | Employee benefit obligations |
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| Defined Benefit Plan Disclosure [Line Items] |
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|
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| Discount rate – benefit obligations |
5.75%
|
5.06%
|
|
| Annual salary increase, benefit obligations |
4.60%
|
4.60%
|
|
| Georgia Power | Other postretirement benefit plans |
|
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| 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 |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate, net periodic benefit costs |
4.89%
|
5.07%
|
2.30%
|
| Georgia Power | Other postretirement benefit plans | Discount rate – service costs |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate, net periodic benefit costs |
5.16%
|
5.34%
|
3.27%
|
| Georgia Power | Other postretirement benefit plans | Employee benefit obligations |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate – benefit obligations |
5.61%
|
4.98%
|
|
| Annual salary increase, benefit obligations |
4.60%
|
4.60%
|
|
| Mississippi Power | Pension plans |
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|
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| 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 |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate, net periodic benefit costs |
4.93%
|
5.12%
|
2.54%
|
| Mississippi Power | Pension plans | Discount rate – service costs |
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|
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate, net periodic benefit costs |
5.19%
|
5.37%
|
3.35%
|
| Mississippi Power | Pension plans | Employee benefit obligations |
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate – benefit obligations |
5.76%
|
5.06%
|
|
| Annual salary increase, benefit obligations |
4.60%
|
4.60%
|
|
| Mississippi Power | Other postretirement benefit plans |
|
|
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| 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 |
|
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| 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 |
|
|
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| Defined Benefit Plan Disclosure [Line Items] |
|
|
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| Discount rate, net periodic benefit costs |
5.16%
|
5.33%
|
3.26%
|
| Mississippi Power | Other postretirement benefit plans | Employee benefit obligations |
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| 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 |
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|
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| 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 |
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|
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| 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 |
|
|
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| 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 |
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|
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| 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 |
|
|
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| 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%
|
|