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RETIREMENT BENEFITS (Tables) | 12 Months Ended
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Dec. 31, 2023
Retirement Benefits [Abstract] |
Summary of actuarial assumptions | The weighted average rates assumed in the actuarial calculations used to determine both the net periodic costs for the pension and other postretirement benefit plans for the following year and the benefit obligations as of the measurement date are presented below.
| 2023
Assumptions used to determine net periodic costs: | Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
Pension plans |  |  |  |  |  |
Discount rate – benefit obligations | 5.25 | % | 5.26 | % | 5.25 | % | 5.25 | % | 5.31 | % | 5.24 | %
Discount rate – interest costs | 5.13 |  | 5.14 |  | 5.12 |  | 5.12 |  | 5.19 |  | 5.12 |
Discount rate – service costs | 5.36 |  | 5.38 |  | 5.38 |  | 5.37 |  | 5.37 |  | 5.31 |
Expected long-term return on plan assets | 8.40 |  | 8.40 |  | 8.40 |  | 8.40 |  | 8.40 |  | 8.40 |
Annual salary increase | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |
Other postretirement benefit plans |  |  |  |  |  |
Discount rate – benefit obligations | 5.18 | % | 5.20 | % | 5.17 | % | 5.17 | % | 5.24 | % | 5.16 | %
Discount rate – interest costs | 5.08 |  | 5.09 |  | 5.07 |  | 5.08 |  | 5.12 |  | 5.07 |
Discount rate – service costs | 5.34 |  | 5.35 |  | 5.34 |  | 5.33 |  | 5.33 |  | 5.33 |
Expected long-term return on plan assets | 7.67 |  | 7.95 |  | 7.49 |  | 7.43 |  | — |  | 6.59 |
Annual salary increase | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |
| 2022
Assumptions used to determine net periodic costs: | Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
Pension plans |  |  |  |  |  |
Discount rate – benefit obligations | 3.09 | % | 3.12 | % | 3.07 | % | 3.07 | % | 3.21 | % | 3.04 | %
Discount rate – interest costs | 2.55 |  | 2.58 |  | 2.51 |  | 2.54 |  | 2.79 |  | 2.53 |
Discount rate – service costs | 3.34 |  | 3.36 |  | 3.37 |  | 3.35 |  | 3.36 |  | 3.21 |
Expected long-term return on plan assets | 8.25 |  | 8.25 |  | 8.25 |  | 8.25 |  | 8.25 |  | 8.25 |
Annual salary increase | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |
Other postretirement benefit plans |  |  |  |  |  |
Discount rate – benefit obligations | 2.90 | % | 2.95 | % | 2.87 | % | 2.88 | % | 3.07 | % | 2.82 | %
Discount rate – interest costs | 2.32 |  | 2.38 |  | 2.30 |  | 2.27 |  | 2.55 |  | 2.17 |
Discount rate – service costs | 3.26 |  | 3.30 |  | 3.27 |  | 3.26 |  | 3.25 |  | 3.22 |
Expected long-term return on plan assets | 7.21 |  | 7.54 |  | 6.88 |  | 7.22 |  | — |  | 6.08 |
Annual salary increase | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |
| 2021
Assumptions used to determine net periodic costs: | Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
Pension plans |  |  |  |  |  |
Discount rate – benefit obligations | 2.81 | % | 2.85 | % | 2.79 | % | 2.80 | % | 2.99 | % | 2.75 | %
Discount rate – interest costs | 2.13 |  | 2.17 |  | 2.09 |  | 2.12 |  | 2.46 |  | 2.10 |
Discount rate – service costs | 3.18 |  | 3.23 |  | 3.21 |  | 3.20 |  | 3.22 |  | 2.97 |
Expected long-term return on plan assets | 8.25 |  | 8.25 |  | 8.25 |  | 8.25 |  | 8.25 |  | 8.25 |
Annual salary increase | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |
Other postretirement benefit plans |  |  |  |  |  |
Discount rate – benefit obligations | 2.56 | % | 2.63 | % | 2.52 | % | 2.53 | % | 2.78 | % | 2.46 | %
Discount rate – interest costs | 1.84 |  | 1.91 |  | 1.82 |  | 1.78 |  | 2.12 |  | 1.64 |
Discount rate – service costs | 3.07 |  | 3.13 |  | 3.08 |  | 3.06 |  | 3.05 |  | 3.01 |
Expected long-term return on plan assets | 7.09 |  | 7.18 |  | 6.84 |  | 6.98 |  | — |  | 6.54 |
Annual salary increase | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |
| 2023
Assumptions used to determine benefit obligations: | Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
Pension plans |  |  |  |  |  |
Discount rate | 5.07 | % | 5.08 | % | 5.06 | % | 5.06 | % | 5.14 | % | 5.05 | %
Annual salary increase | 4.60 |  | 4.60 |  | 4.60 |  | 4.60 |  | 4.60 |  | 4.60 |
Other postretirement benefit plans |  |  |  |  |  |
Discount rate | 4.99 | % | 5.01 | % | 4.98 | % | 4.98 | % | 5.06 | % | 4.98 | %
Annual salary increase | 4.60 |  | 4.60 |  | 4.60 |  | 4.60 |  | 4.60 |  | 4.60 |
| 2022
Assumptions used to determine benefit obligations: | Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
Pension plans |  |  |  |  |  |
Discount rate | 5.25 | % | 5.26 | % | 5.25 | % | 5.25 | % | 5.31 | % | 5.24 | %
Annual salary increase | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |
Other postretirement benefit plans |  |  |  |  |  |
Discount rate | 5.18 | % | 5.20 | % | 5.17 | % | 5.17 | % | 5.24 | % | 5.16 | %
Annual salary increase | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |  | 4.80 |
Schedule of health care cost trend rates | The weighted average medical care cost trend rates used in measuring the APBO for the Registrants at December 31, 2023 were as follows:
| Initial Cost Trend Rate |  | Ultimate Cost Trend Rate |  | Year That Ultimate Rate is Reached
Pre-65 | 7.00 | % |  | 4.50 | % |  | 2032
Post-65 medical | 5.50 |  |  | 4.50 |  |  | 2032
Post-65 prescription | 8.50 |  |  | 4.50 |  |  | 2032
Schedule of accumulated and projected benefit obligations | The total accumulated benefit obligation for the pension plans at December 31, 2023 and 2022 was as follows:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
December 31, 2023 | $ | 11,991 |  | $ | 2,746 |  | $ | 3,674 |  | $ | 546 |  | $ | 145 |  | $ | 808 |
December 31, 2022 | 11,422 |  | 2,601 |  | 3,534 |  | 520 |  | 135 |  | 801 |
The projected benefit obligations for the qualified and non-qualified pension plans at December 31, 2023 are shown in the following table. All pension plan assets are related to the qualified pension plan.
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
Projected benefit obligations: |  |  |  |  |  |
Qualified pension plan | $ | 12,540 |  | $ | 2,959 |  | $ | 3,865 |  | $ | 569 |  | $ | 154 |  | $ | 822 |
Non-qualified pension plan | 713 |  | 117 |  | 145 |  | 29 |  | 22 |  | 60 |
Changes in projected benefit obligations and fair value of plan assets | Changes in the projected benefit obligations and the fair value of plan assets during the plan years ended December 31, 2023 and 2022 were as follows:
| 2023
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
Change in benefit obligation |  |  |  |  |  |
Benefit obligation at beginning of year | $ | 12,602 |  | $ | 2,906 |  | $ | 3,851 |  | $ | 569 |  | $ | 163 |  | $ | 868 |
Service cost | 275 |  | 64 |  | 68 |  | 11 |  | 6 |  | 24 |
Interest cost | 626 |  | 145 |  | 191 |  | 28 |  | 8 |  | 42 |
Benefits paid | (744) |  | (155) |  | (224) |  | (32) |  | (6) |  | (104) |
Actuarial loss | 493 |  | 116 |  | 123 |  | 23 |  | 6 |  | 52 |
Balance at end of year | 13,252 |  | 3,076 |  | 4,009 |  | 599 |  | 177 |  | 882 |
Change in plan assets |  |  |  |  |  |
Fair value of plan assets at beginning of year | 14,218 |  | 3,427 |  | 4,456 |  | 649 |  | 178 |  | 1,002 |
Actual return on plan assets | 1,092 |  | 260 |  | 331 |  | 50 |  | 12 |  | 79 |
Employer contributions | 52 |  | 11 |  | 9 |  | 2 |  | 2 |  | 3 |
Benefits paid | (744) |  | (154) |  | (225) |  | (32) |  | (7) |  | (104) |
Fair value of plan assets at end of year | 14,618 |  | 3,544 |  | 4,571 |  | 669 |  | 185 |  | 980 |
Accrued asset | $ | 1,366 |  | $ | 468 |  | $ | 562 |  | $ | 70 |  | $ | 8 |  | $ | 98 |
| 2022
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
Change in benefit obligation |  |  |  |  |  |
Benefit obligation at beginning of year | $ | 16,382 |  | $ | 3,806 |  | $ | 5,012 |  | $ | 743 |  | $ | 222 |  | $ | 1,134 |
Service cost | 412 |  | 99 |  | 103 |  | 17 |  | 9 |  | 34 |
Interest cost | 408 |  | 96 |  | 123 |  | 18 |  | 6 |  | 28 |
Benefits paid | (692) |  | (144) |  | (226) |  | (30) |  | (5) |  | (75) |
Actuarial gain | (3,908) |  | (951) |  | (1,161) |  | (179) |  | (69) |  | (253) |
Balance at end of year | 12,602 |  | 2,906 |  | 3,851 |  | 569 |  | 163 |  | 868 |
Change in plan assets |  |  |  |  |  |
Fair value of plan assets at beginning of year | 17,225 |  | 4,141 |  | 5,415 |  | 786 |  | 213 |  | 1,241 |
Actual loss on plan assets | (2,376) |  | (579) |  | (753) |  | (110) |  | (31) |  | (167) |
Employer contributions | 61 |  | 9 |  | 20 |  | 3 |  | 1 |  | 3 |
Benefits paid | (692) |  | (144) |  | (226) |  | (30) |  | (5) |  | (75) |
Fair value of plan assets at end of year | 14,218 |  | 3,427 |  | 4,456 |  | 649 |  | 178 |  | 1,002 |
Accrued asset | $ | 1,616 |  | $ | 521 |  | $ | 605 |  | $ | 80 |  | $ | 15 |  | $ | 134 |
Amounts recognized in balance sheets | Amounts recognized in the balance sheets at December 31, 2023 and 2022 related to the Registrants' pension plans consist of the following:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
December 31, 2023: |  |  |  |  |  |
Prepaid pension costs(a) | $ | 2,079 |  | $ | 585 |  | $ | 706 |  | $ | 99 |  | $ | 31 |  | $ | 158 |
Other regulatory assets, deferred(b) | 2,960 |  | 821 |  | 1,051 |  | 152 |  | — |  | 143 |
Other current liabilities | (64) |  | (11) |  | (13) |  | (2) |  | (2) |  | (3) |
Employee benefit obligations(c) | (649) |  | (106) |  | (131) |  | (27) |  | (21) |  | (58) |
Other regulatory liabilities, deferred | (47) |  | — |  | — |  | — |  | — |  | — |
AOCI | 79 |  | — |  | — |  | — |  | 20 |  | (45) |
December 31, 2022: |  |  |  |  |  |
Prepaid pension costs(a) | $ | 2,290 |  | $ | 629 |  | $ | 738 |  | $ | 108 |  | $ | 37 |  | $ | 183 |
Other regulatory assets, deferred(b) | 2,455 |  | 679 |  | 887 |  | 123 |  | — |  | 111 |
Other current liabilities | (56) |  | (10) |  | (12) |  | (2) |  | (2) |  | (3) |
Employee benefit obligations(c) | (618) |  | (98) |  | (121) |  | (26) |  | (20) |  | (42) |
Other regulatory liabilities, deferred | (85) |  | — |  | — |  | — |  | — |  | — |
AOCI | 24 |  | — |  | — |  | — |  | 11 |  | (75) |
(a)Included in prepaid pension and other postretirement benefit costs on Alabama Power's balance sheet and other deferred charges and assets on Southern Power's consolidated balance sheet. (b)Amounts for Southern Company exclude regulatory assets of $173 million and $190 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' pension plans prior to its acquisition by Southern Company. (c)Included in other deferred credits and liabilities on Southern Power's consolidated balance sheets. Presented below are the amounts included in regulatory assets at December 31, 2023 and 2022 related to the portion of the defined benefit pension plan attributable to Southern Company, the traditional electric operating companies, and Southern Company Gas that had not yet been recognized in net periodic pension cost.
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Company Gas
| (in millions)
Balance at December 31, 2023 |  |  |  |  |
Regulatory assets: |  |  |  |  |
Prior service cost | $ | 9 |  | $ | 4 |  | $ | 6 |  | $ | 1 |  | $ | (7) |
Net loss | 2,904 |  | 817 |  | 1,045 |  | 151 |  | 100 |
Regulatory amortization | — |  | — |  | — |  | — |  | 50 |
Total regulatory assets(*) | $ | 2,913 |  | $ | 821 |  | $ | 1,051 |  | $ | 152 |  | $ | 143 |
Balance at December 31, 2022 |  |  |  |  |
Regulatory assets: |  |  |  |  |
Prior service cost | $ | 10 |  | $ | 4 |  | $ | 7 |  | $ | 1 |  | $ | (9) |
Net loss | 2,361 |  | 675 |  | 880 |  | 122 |  | 66 |
Regulatory amortization | — |  | — |  | — |  | — |  | 54 |
Total regulatory assets(*) | $ | 2,371 |  | $ | 679 |  | $ | 887 |  | $ | 123 |  | $ | 111 |
(*)Amounts for Southern Company exclude regulatory assets of $173 million and $190 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' pension plans prior to its acquisition by Southern Company. Amounts recognized in the balance sheets at December 31, 2023 and 2022 related to the Registrants' other postretirement benefit plans consist of the following:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
December 31, 2023: |  |  |  |  |  |
Prepaid other postretirement benefit costs(a) | $ | — |  | $ | 74 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |
Other regulatory assets, deferred(b) | 23 |  | — |  | 11 |  | — |  | — |  | — |
Other current liabilities | (6) |  | — |  | — |  | — |  | (1) |  | — |
Employee benefit obligations(c) | (285) |  | — |  | (79) |  | (32) |  | (8) |  | (44) |
Other regulatory liabilities, deferred | (231) |  | (48) |  | (85) |  | (10) |  | — |  | (68) |
AOCI | (9) |  | — |  | — |  | — |  | 1 |  | (10) |
December 31, 2022: |  |  |  |  |  |
Prepaid other postretirement benefit costs(a) | $ | — |  | $ | 28 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |
Other regulatory assets, deferred(b) | 34 |  | — |  | 19 |  | — |  | — |  | — |
Other current liabilities | (6) |  | — |  | — |  | — |  | (1) |  | — |
Employee benefit obligations(c) | (437) |  | — |  | (146) |  | (35) |  | (8) |  | (66) |
Other regulatory liabilities, deferred | (170) |  | (21) |  | (58) |  | (9) |  | — |  | (58) |
AOCI | (4) |  | — |  | — |  | — |  | — |  | (2) |
(a)Included in prepaid pension and other postretirement benefit costs on Alabama Power's balance sheet. (b)Amounts for Southern Company exclude regulatory assets of $24 million and $32 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' other postretirement benefit plans prior to its acquisition by Southern Company. (c)Included in other deferred credits and liabilities on Southern Power's consolidated balance sheets. Presented below are the amounts included in net regulatory assets (liabilities) at December 31, 2023 and 2022 related to the other postretirement benefit plans of Southern Company, the traditional electric operating companies, and Southern Company Gas that had not yet been recognized in net periodic other postretirement benefit cost.
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Company Gas
| (in millions)
Balance at December 31, 2023: |  |  |  |  |
Regulatory assets (liabilities): |  |  |  |  |
Prior service cost | $ | 13 |  | $ | 4 |  | $ | 5 |  | $ | 1 |  | $ | — |
Net gain | (216) |  | (52) |  | (79) |  | (11) |  | (64) |
Regulatory amortization | — |  | — |  | — |  | — |  | (4) |
Total regulatory assets (liabilities)(*) | $ | (203) |  | $ | (48) |  | $ | (74) |  | $ | (10) |  | $ | (68) |
Balance at December 31, 2022: |  |  |  |  |
Regulatory assets (liabilities): |  |  |  |  |
Prior service cost | $ | 14 |  | $ | 4 |  | $ | 6 |  | $ | 1 |  | $ | 1 |
Net gain | (150) |  | (25) |  | (45) |  | (10) |  | (64) |
Regulatory amortization | — |  | — |  | — |  | — |  | 5 |
Total regulatory assets (liabilities)(*) | $ | (136) |  | $ | (21) |  | $ | (39) |  | $ | (9) |  | $ | (58) |
(*)Amounts for Southern Company exclude regulatory assets of $24 million and $32 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' other postretirement benefit plans prior to its acquisition by Southern Company.
Changes in balances of regulatory assets and regulatory liabilities related to defined benefit pension plans | The changes in the balance of regulatory assets related to the portion of the defined benefit pension plan attributable to Southern Company, the traditional electric operating companies, and Southern Company Gas for the years ended December 31, 2023 and 2022 are presented in the following table:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Company Gas
| (in millions)
Regulatory assets (liabilities):(*) |  |  |  |  |
Balance at December 31, 2021 | $ | 2,801 |  | $ | 809 |  | $ | 971 |  | $ | 146 |  | $ | 91 |
Net (gain) loss | (183) |  | (67) |  | (9) |  | (12) |  | 27 |
Reclassification adjustments: |  |  |  |  |
Amortization of prior service costs | (1) |  | (1) |  | (1) |  | — |  | 2 |
Amortization of net gain (loss) | (246) |  | (62) |  | (74) |  | (11) |  | 1 |
Amortization of regulatory assets(*) | — |  | — |  | — |  | — |  | (10) |
Total reclassification adjustments | (247) |  | (63) |  | (75) |  | (11) |  | (7) |
Total change | (430) |  | (130) |  | (84) |  | (23) |  | 20 |
Balance at December 31, 2022 | $ | 2,371 |  | $ | 679 |  | $ | 887 |  | $ | 123 |  | $ | 111 |
Net loss | 576 |  | 153 |  | 178 |  | 31 |  | 34 |
Reclassification adjustments: |  |  |  |  |
Amortization of prior service costs | (1) |  | (1) |  | (1) |  | — |  | 2 |
Amortization of net loss | (33) |  | (10) |  | (13) |  | (2) |  | — |
Amortization of regulatory assets(*) | — |  | — |  | — |  | — |  | (4) |
Total reclassification adjustments | (34) |  | (11) |  | (14) |  | (2) |  | (2) |
Total change | 542 |  | 142 |  | 164 |  | 29 |  | 32 |
Balance at December 31, 2023 | $ | 2,913 |  | $ | 821 |  | $ | 1,051 |  | $ | 152 |  | $ | 143 |
(*)Amounts for Southern Company exclude regulatory assets of $173 million and $190 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' pension plans prior to its acquisition by Southern Company. The changes in the balance of net regulatory assets (liabilities) related to the other postretirement benefit plans for the plan years ended December 31, 2023 and 2022 are presented in the following table:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Company Gas
| (in millions)
Net regulatory assets (liabilities):(*) |  |  |  |  |
Balance at December 31, 2021 | $ | (74) |  | $ | (62) |  | $ | (10) |  | $ | 1 |  | $ | (34) |
Net (gain) loss | (64) |  | 41 |  | (27) |  | (10) |  | (13) |
Reclassification adjustments: |  |  |  |  |
Amortization of prior service costs | 1 |  | — |  | — |  | — |  | — |
Amortization of net gain (loss) | 1 |  | — |  | (2) |  | — |  | — |
Amortization of regulatory assets(*) | — |  | — |  | — |  | — |  | (11) |
Total reclassification adjustments | 2 |  | — |  | (2) |  | — |  | (11) |
Total change | (62) |  | 41 |  | (29) |  | (10) |  | (24) |
Balance at December 31, 2022 | $ | (136) |  | $ | (21) |  | $ | (39) |  | $ | (9) |  | $ | (58) |
Net gain | (77) |  | (30) |  | (38) |  | (1) |  | — |
Reclassification adjustments: |  |  |  |  |
Amortization of prior service costs | (1) |  | — |  | (1) |  | — |  | — |
Amortization of net gain | 6 |  | 3 |  | 4 |  | — |  | — |
Amortization of regulatory assets(*) | — |  | — |  | — |  | — |  | (10) |
Total reclassification adjustments | 5 |  | 3 |  | 3 |  | — |  | (10) |
Total change | (72) |  | (27) |  | (35) |  | (1) |  | (10) |
Balance at December 31, 2023 | $ | (208) |  | $ | (48) |  | $ | (74) |  | $ | (10) |  | $ | (68) |
(*)Amounts for Southern Company exclude regulatory assets of $24 million and $32 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' other postretirement benefit plans prior to its acquisition by Southern Company.
Amounts included in AOCI related to defined benefit pension plans | Presented below are the amounts included in AOCI at December 31, 2023 and 2022 related to the portion of the defined benefit pension plan attributable to Southern Company, Southern Power, and Southern Company Gas that had not yet been recognized in net periodic pension cost.
| Southern Company | Southern Power | Southern Company Gas
| (in millions)
Balance at December 31, 2023 |  |  |
AOCI: |  |  |
Prior service cost | $ | (1) |  | $ | — |  | $ | (2) |
Net (gain) loss | 80 |  | 20 |  | (43) |
Total AOCI | $ | 79 |  | $ | 20 |  | $ | (45) |
Balance at December 31, 2022 |  |  |
AOCI: |  |  |
Prior service cost | $ | (2) |  | $ | — |  | $ | (3) |
Net (gain) loss | 26 |  | 11 |  | (72) |
Total AOCI | $ | 24 |  | $ | 11 |  | $ | (75) |
Presented below are the amounts included in AOCI at December 31, 2023 and 2022 related to the other postretirement benefit plans of Southern Company, Southern Power, and Southern Company Gas that had not yet been recognized in net periodic other postretirement benefit cost.
| Southern Company | Southern Power | Southern Company Gas
| (in millions)
Balance at December 31, 2023 |  |  |
AOCI: |  |  |
Prior service cost | $ | 1 |  | $ | — |  | $ | — |
Net (gain) loss | (10) |  | 1 |  | (10) |
Total AOCI | $ | (9) |  | $ | 1 |  | $ | (10) |
Balance at December 31, 2022 |  |  |
AOCI: |  |  |
Prior service cost | $ | 1 |  | $ | — |  | $ | — |
Net (gain) loss | (5) |  | — |  | (2) |
Total AOCI | $ | (4) |  | $ | — |  | $ | (2) |
Components of OCI related to defined benefit pension plan | The components of OCI related to the portion of the defined benefit pension plan attributable to Southern Company, Southern Power, and Southern Company Gas for the years ended December 31, 2023 and 2022 are presented in the following table:
| Southern Company | Southern Power | Southern Company Gas
| (in millions)
AOCI: |  |  |
Balance at December 31, 2021 | $ | 100 |  | $ | 35 |  | $ | (45) |
Net gain | (82) |  | (22) |  | (30) |
Reclassification adjustments: |  |  |
Amortization of net gain (loss) | 6 |  | (2) |  | — |
Total change | (76) |  | (24) |  | (30) |
Balance at December 31, 2022 | $ | 24 |  | $ | 11 |  | $ | (75) |
Net loss | 62 |  | 9 |  | 29 |
Reclassification adjustments: |  |  |
Amortization of prior service costs | 1 |  | — |  | 1 |
Amortization of net loss | (8) |  | — |  | — |
Total reclassification adjustments | (7) |  | — |  | 1 |
Total change | 55 |  | 9 |  | 30 |
Balance at December 31, 2023 | $ | 79 |  | $ | 20 |  | $ | (45) |
The components of OCI related to the other postretirement benefit plans for the plan years ended December 31, 2023 and 2022 are presented in the following table:
| Southern Company | Southern Power | Southern Company Gas
| (in millions)
AOCI: |  |  |
Balance at December 31, 2021 | $ | — |  | $ | 2 |  | $ | (5) |
Net gain | (3) |  | (2) |  | — |
Reclassification adjustments: |  |  |
Amortization of net gain (loss) | (1) |  | — |  | 3 |
Total change | (4) |  | (2) |  | 3 |
Balance at December 31, 2022 | $ | (4) |  | $ | — |  | $ | (2) |
Net (gain) loss | (12) |  | 1 |  | — |
Reclassification adjustments: |  |  |
Amortization of net gain (loss) | 7 |  | — |  | (8) |
Total change | (5) |  | 1 |  | (8) |
Balance at December 31, 2023 | $ | (9) |  | $ | 1 |  | $ | (10) |
Components of net periodic benefit cost | Components of net periodic pension cost for the Registrants were as follows:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
2023 |  |  |  |  |  |
Service cost | $ | 275 |  | $ | 64 |  | $ | 68 |  | $ | 11 |  | $ | 6 |  | $ | 24 |
Interest cost | 626 |  | 145 |  | 191 |  | 28 |  | 8 |  | 42 |
Expected return on plan assets | (1,229) |  | (297) |  | (385) |  | (56) |  | (15) |  | (85) |
Recognized net (gain) loss | 32 |  | 9 |  | 13 |  | 2 |  | — |  | (5) |
Net amortization | — |  | 1 |  | 1 |  | — |  | — |  | 15 |
Prior service cost | — |  | — |  | — |  | — |  | — |  | (3) |
Net periodic pension cost (income) | $ | (296) |  | $ | (78) |  | $ | (112) |  | $ | (15) |  | $ | (1) |  | $ | (12) |
2022 |  |  |  |  |  |
Service cost | $ | 412 |  | $ | 99 |  | $ | 103 |  | $ | 17 |  | $ | 9 |  | $ | 34 |
Interest cost | 408 |  | 96 |  | 123 |  | 18 |  | 6 |  | 28 |
Expected return on plan assets | (1,265) |  | (306) |  | (399) |  | (57) |  | (15) |  | (91) |
Recognized net loss | 240 |  | 62 |  | 75 |  | 11 |  | 2 |  | 8 |
Net amortization | — |  | 1 |  | 1 |  | — |  | — |  | 15 |
Prior service cost | — |  | — |  | — |  | — |  | — |  | (3) |
Net periodic pension cost (income) | $ | (205) |  | $ | (48) |  | $ | (97) |  | $ | (11) |  | $ | 2 |  | $ | (9) |
2021 |  |  |  |  |  |
Service cost | $ | 434 |  | $ | 102 |  | $ | 112 |  | $ | 18 |  | $ | 10 |  | $ | 37 |
Interest cost | 346 |  | 82 |  | 104 |  | 16 |  | 5 |  | 24 |
Expected return on plan assets | (1,191) |  | (287) |  | (375) |  | (55) |  | (14) |  | (86) |
Recognized net loss | 314 |  | 82 |  | 100 |  | 15 |  | 3 |  | 13 |
Net amortization | 1 |  | 1 |  | 1 |  | — |  | — |  | 15 |
Prior service cost | — |  | — |  | — |  | — |  | — |  | (3) |
Net periodic pension cost (income) | $ | (96) |  | $ | (20) |  | $ | (58) |  | $ | (6) |  | $ | 4 |  | $ | — |
Components of the other postretirement benefit plans' net periodic cost for the Registrants were as follows:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
2023 |  |  |  |  |  |
Service cost | $ | 15 |  | $ | 4 |  | $ | 4 |  | $ | 1 |  | $ | — |  | $ | 1 |
Interest cost | 70 |  | 17 |  | 25 |  | 3 |  | — |  | 9 |
Expected return on plan assets | (83) |  | (33) |  | (29) |  | (3) |  | 1 |  | (10) |
Net amortization | (11) |  | (3) |  | (3) |  | — |  | — |  | 6 |
Net periodic postretirement benefit cost (income) | $ | (9) |  | $ | (15) |  | $ | (3) |  | $ | 1 |  | $ | 1 |  | $ | 6 |
2022 |  |  |  |  |  |
Service cost | $ | 23 |  | $ | 6 |  | $ | 6 |  | $ | 1 |  | $ | — |  | $ | 1 |
Interest cost | 42 |  | 10 |  | 15 |  | 2 |  | — |  | 5 |
Expected return on plan assets | (80) |  | (32) |  | (28) |  | (2) |  | 1 |  | (9) |
Net amortization | (1) |  | — |  | 2 |  | — |  | — |  | 6 |
Net periodic postretirement benefit cost (income) | $ | (16) |  | $ | (16) |  | $ | (5) |  | $ | 1 |  | $ | 1 |  | $ | 3 |
2021 |  |  |  |  |  |
Service cost | $ | 24 |  | $ | 6 |  | $ | 7 |  | $ | 1 |  | $ | — |  | $ | 2 |
Interest cost | 35 |  | 9 |  | 12 |  | 1 |  | — |  | 4 |
Expected return on plan assets | (76) |  | (30) |  | (26) |  | (1) |  | 1 |  | (10) |
Net amortization | 2 |  | — |  | 2 |  | — |  | — |  | 6 |
Net periodic postretirement benefit cost (income) | $ | (15) |  | $ | (15) |  | $ | (5) |  | $ | 1 |  | $ | 1 |  | $ | 2 |
Estimated pension benefit payments | At December 31, 2023, estimated benefit payments were as follows:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
Benefit Payments: |  |  |  |  |  |
2024 | $ | 748 |  | $ | 164 |  | $ | 241 |  | $ | 33 |  | $ | 7 |  | $ | 57 |
2025 | 776 |  | 171 |  | 248 |  | 34 |  | 7 |  | 59 |
2026 | 801 |  | 177 |  | 254 |  | 36 |  | 8 |  | 60 |
2027 | 822 |  | 182 |  | 257 |  | 37 |  | 8 |  | 62 |
2028 | 840 |  | 187 |  | 260 |  | 38 |  | 7 |  | 64 |
2029 to 2033 | 4,417 |  | 988 |  | 1,337 |  | 201 |  | 47 |  | 336 |
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
Benefit payments: |  |  |  |  |  |
2024 | $ | 111 |  | $ | 24 |  | $ | 40 |  | $ | 5 |  | $ | 1 |  | $ | 17 |
2025 | 109 |  | 24 |  | 39 |  | 5 |  | 1 |  | 17 |
2026 | 108 |  | 24 |  | 38 |  | 5 |  | 1 |  | 16 |
2027 | 108 |  | 24 |  | 38 |  | 5 |  | 1 |  | 16 |
2028 | 108 |  | 25 |  | 38 |  | 4 |  | 1 |  | 15 |
2029 to 2033 | 523 |  | 123 |  | 188 |  | 21 |  | 1 |  | 64 |
Changes in the APBO and the fair value of plan assets | Changes in the APBO and the fair value of the Registrants' plan assets during the plan years ended December 31, 2023 and 2022 were as follows:
| 2023
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
Change in benefit obligation |  |  |  |  |  |
Benefit obligation at beginning of year | $ | 1,441 |  | $ | 344 |  | $ | 514 |  | $ | 59 |  | $ | 9 |  | $ | 179 |
Service cost | 15 |  | 4 |  | 4 |  | 1 |  | — |  | 1 |
Interest cost | 70 |  | 17 |  | 25 |  | 3 |  | — |  | 9 |
Benefits paid | (107) |  | (24) |  | (36) |  | (4) |  | (1) |  | (18) |
Actuarial (gain) loss | (33) |  | (12) |  | (18) |  | (2) |  | 1 |  | 1 |
Balance at end of year | 1,386 |  | 329 |  | 489 |  | 57 |  | 9 |  | 172 |
Change in plan assets |  |  |  |  |  |
Fair value of plan assets at beginning of year | 998 |  | 372 |  | 368 |  | 24 |  | — |  | 113 |
Actual return on plan assets | 131 |  | 52 |  | 51 |  | 2 |  | — |  | 19 |
Employer contributions | 73 |  | 3 |  | 27 |  | 3 |  | 1 |  | 14 |
Benefits paid | (107) |  | (24) |  | (36) |  | (4) |  | (1) |  | (18) |
Fair value of plan assets at end of year | 1,095 |  | 403 |  | 410 |  | 25 |  | — |  | 128 |
Accrued asset (liability) | $ | (291) |  | $ | 74 |  | $ | (79) |  | $ | (32) |  | $ | (9) |  | $ | (44) |
| 2022
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
Change in benefit obligation |  |  |  |  |  |
Benefit obligation at beginning of year | $ | 1,849 |  | $ | 440 |  | $ | 656 |  | $ | 76 |  | $ | 11 |  | $ | 237 |
Service cost | 23 |  | 6 |  | 6 |  | 1 |  | — |  | 1 |
Interest cost | 42 |  | 10 |  | 15 |  | 2 |  | — |  | 5 |
Benefits paid | (109) |  | (23) |  | (38) |  | (4) |  | (1) |  | (18) |
Actuarial gain | (365) |  | (89) |  | (125) |  | (16) |  | (1) |  | (46) |
Retiree drug subsidy | 1 |  | — |  | — |  | — |  | — |  | — |
Balance at end of year | 1,441 |  | 344 |  | 514 |  | 59 |  | 9 |  | 179 |
Change in plan assets |  |  |  |  |  |
Fair value of plan assets at beginning of year | 1,251 |  | 489 |  | 450 |  | 29 |  | — |  | 143 |
Actual loss on plan assets | (218) |  | (98) |  | (71) |  | (4) |  | — |  | (25) |
Employer contributions | 73 |  | 4 |  | 27 |  | 3 |  | 1 |  | 13 |
Benefits paid | (108) |  | (23) |  | (38) |  | (4) |  | (1) |  | (18) |
Fair value of plan assets at end of year | 998 |  | 372 |  | 368 |  | 24 |  | — |  | 113 |
Accrued asset (liability) | $ | (443) |  | $ | 28 |  | $ | (146) |  | $ | (35) |  | $ | (9) |  | $ | (66) |
Summary of investment strategies and benefit plan asset fair values | A description of the major asset classes that the pension and other postretirement benefit plans are comprised of, along with the valuation methods used for fair value measurement, is provided below:
Description | Valuation Methodology
Domestic equity: A mix of large and small capitalization stocks with generally an equal distribution of value and growth attributes, managed both actively and through passive index approaches. International equity: A mix of large and small capitalization growth and value stocks with developed and emerging markets exposure, managed both actively and through fundamental indexing approaches. | Domestic and international equities such as common stocks, American depositary receipts, and real estate investment trusts that trade on public exchanges are classified as Level 1 investments and are valued at the closing price in the active market. Equity funds with unpublished prices that are comprised of publicly traded securities (such as commingled/pooled funds) are also valued at the closing price in the active market, but are classified as Level 2.
Fixed income: A mix of domestic and international bonds. | Investments in fixed income securities, including fixed income pooled funds, are generally classified as Level 2 investments and are valued based on prices reported in the market place. Additionally, the value of fixed income securities takes into consideration certain items such as broker quotes, spreads, yield curves, interest rates, and discount rates that apply to the term of a specific instrument.
Trust-owned life insurance (TOLI): Investments of taxable trusts aimed at minimizing the impact of taxes on the portfolio. | Investments in TOLI policies are classified as Level 2 investments and are valued based on the underlying investments held in the policy's separate accounts. The underlying assets are equity and fixed income pooled funds that are comprised of Level 1 and Level 2 securities.
Real estate: Investments in equity or debt of real properties and in publicly traded real estate securities. Special situations: Investments in opportunistic strategies with the objective of diversifying and enhancing returns and exploiting short-term inefficiencies, as well as investments in promising new strategies of a longer-term nature. Private equity: Investments in private or public securities typically through privately-negotiated and/or structured transactions, including leveraged buyouts, venture capital, and distressed debt. Private credit: Investments focused on debt instruments, of which returns are driven by income rather than capital appreciation. Infrastructure: Investments in real assets, typically with long-term, predictable, and stable cash flows and a meaningful income component. | Investments in real estate, special situations, private equity, private credit, and infrastructure are typically invested in private partnerships and/or other pooled vehicles (Funds) which are generally classified as Net Asset Value as a Practical Expedient, since the Funds and underlying assets are not publicly traded and/or often have liquidity restrictions. The managers of the Funds value the assets using various inputs and techniques depending on the nature of the underlying investments. Techniques may include purchase multiples for comparable transactions, comparable public company trading multiples, discounted cash flow analysis, prevailing market capitalization rates, recent sales of comparable investments, and independent third-party appraisals. The total market value of each of the Funds is determined by aggregating the value of the underlying assets less liabilities.
Fair values of plan assets | The fair values, and actual allocations relative to the target allocations, of the Southern Company system's pension plans at December 31, 2023 and 2022 are presented below.
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs | Significant Unobservable Inputs | Net Asset Value as a Practical Expedient |  | Target Allocation | Actual Allocation
At December 31, 2023: | (Level 1) | (Level 2) | (Level 3) | (NAV) | Total
| (in millions) |  |
Southern Company |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 41 | % | 40 | %
Domestic equity | $ | 1,959 |  | $ | 771 |  | $ | — |  | $ | — |  | $ | 2,730 |  |  |
International equity | 1,947 |  | 1,052 |  | — |  | — |  | 2,999 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 32 |
U.S. Treasury, government, and agency bonds | — |  | 1,973 |  | — |  | — |  | 1,973 |  |  |
Mortgage- and asset-backed securities | — |  | 44 |  | — |  | — |  | 44 |  |  |
Corporate bonds | — |  | 1,724 |  | — |  | — |  | 1,724 |  |  |
Pooled funds | — |  | 777 |  | — |  | — |  | 777 |  |  |
Cash equivalents and other | 371 |  | 58 |  | — |  | — |  | 429 |  |  |
Real estate investments | 369 |  | — |  | — |  | 1,684 |  | 2,053 |  | 12 |  | 14 |
Special situations | — |  | — |  | — |  | 245 |  | 245 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 1,761 |  | 1,761 |  | 9 |  | 12 |
Private credit | — |  | — |  | — |  | 25 |  | 25 |  | 3 |  | — |
Infrastructure | — |  | — |  | — |  | — |  | — |  | 2 |  | — |
Total | $ | 4,646 |  | $ | 6,399 |  | $ | — |  | $ | 3,715 |  | $ | 14,760 |  | 100 | % | 100 | %
Alabama Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 41 | % | 40 | %
Domestic equity | $ | 476 |  | $ | 187 |  | $ | — |  | $ | — |  | $ | 663 |  |  |
International equity | 472 |  | 255 |  | — |  | — |  | 727 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 32 |
U.S. Treasury, government, and agency bonds | — |  | 479 |  | — |  | — |  | 479 |  |  |
Mortgage- and asset-backed securities | — |  | 11 |  | — |  | — |  | 11 |  |  |
Corporate bonds | — |  | 418 |  | — |  | — |  | 418 |  |  |
Pooled funds | — |  | 188 |  | — |  | — |  | 188 |  |  |
Cash equivalents and other | 90 |  | 14 |  | — |  | — |  | 104 |  |  |
Real estate investments | 89 |  | — |  | — |  | 408 |  | 497 |  | 12 |  | 14 |
Special situations | — |  | — |  | — |  | 59 |  | 59 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 427 |  | 427 |  | 9 |  | 12 |
Private credit | — |  | — |  | — |  | 6 |  | 6 |  | 3 |  | — |
Infrastructure | — |  | — |  | — |  | — |  | — |  | 2 |  | — |
Total | $ | 1,127 |  | $ | 1,552 |  | $ | — |  | $ | 900 |  | $ | 3,579 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs | Significant Unobservable Inputs | Net Asset Value as a Practical Expedient |  | Target Allocation | Actual Allocation
At December 31, 2023: | (Level 1) | (Level 2) | (Level 3) | (NAV) | Total
| (in millions) |  |
Georgia Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 41 | % | 40 | %
Domestic equity | $ | 611 |  | $ | 241 |  | $ | — |  | $ | — |  | $ | 852 |  |  |
International equity | 609 |  | 329 |  | — |  | — |  | 938 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 32 |
U.S. Treasury, government, and agency bonds | — |  | 617 |  | — |  | — |  | 617 |  |  |
Mortgage- and asset-backed securities | — |  | 14 |  | — |  | — |  | 14 |  |  |
Corporate bonds | — |  | 539 |  | — |  | — |  | 539 |  |  |
Pooled funds | — |  | 243 |  | — |  | — |  | 243 |  |  |
Cash equivalents and other | 116 |  | 18 |  | — |  | — |  | 134 |  |  |
Real estate investments | 115 |  | — |  | — |  | 527 |  | 642 |  | 12 |  | 14 |
Special situations | — |  | — |  | — |  | 77 |  | 77 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 551 |  | 551 |  | 9 |  | 12 |
Private credit | — |  | — |  | — |  | 8 |  | 8 |  | 3 |  | — |
Infrastructure | — |  | — |  | — |  | — |  | — |  | 2 |  | — |
Total | $ | 1,451 |  | $ | 2,001 |  | $ | — |  | $ | 1,163 |  | $ | 4,615 |  | 100 | % | 100 | %
Mississippi Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 41 | % | 40 | %
Domestic equity | $ | 89 |  | $ | 35 |  | $ | — |  | $ | — |  | $ | 124 |  |  |
International equity | 89 |  | 48 |  | — |  | — |  | 137 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 32 |
U.S. Treasury, government, and agency bonds | — |  | 90 |  | — |  | — |  | 90 |  |  |
Mortgage- and asset-backed securities | — |  | 2 |  | — |  | — |  | 2 |  |  |
Corporate bonds | — |  | 79 |  | — |  | — |  | 79 |  |  |
Pooled funds | — |  | 36 |  | — |  | — |  | 36 |  |  |
Cash equivalents and other | 17 |  | 3 |  | — |  | — |  | 20 |  |  |
Real estate investments | 17 |  | — |  | — |  | 77 |  | 94 |  | 12 |  | 14 |
Special situations | — |  | — |  | — |  | 11 |  | 11 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 81 |  | 81 |  | 9 |  | 12 |
Private credit | — |  | — |  | — |  | 1 |  | 1 |  | 3 |  | — |
Infrastructure | — |  | — |  | — |  | — |  | — |  | 2 |  | — |
Total | $ | 212 |  | $ | 293 |  | $ | — |  | $ | 170 |  | $ | 675 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs | Significant Unobservable Inputs | Net Asset Value as a Practical Expedient |  | Target Allocation | Actual Allocation
At December 31, 2023: | (Level 1) | (Level 2) | (Level 3) | (NAV) | Total
| (in millions) |  |
Southern Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 41 | % | 40 | %
Domestic equity | $ | 24 |  | $ | 10 |  | $ | — |  | $ | — |  | $ | 34 |  |  |
International equity | 25 |  | 13 |  | — |  | — |  | 38 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 32 |
U.S. Treasury, government, and agency bonds | — |  | 25 |  | — |  | — |  | 25 |  |  |
Mortgage- and asset-backed securities | — |  | 1 |  | — |  | — |  | 1 |  |  |
Corporate bonds | — |  | 22 |  | — |  | — |  | 22 |  |  |
Pooled funds | — |  | 10 |  | — |  | — |  | 10 |  |  |
Cash equivalents and other | 5 |  | 1 |  | — |  | — |  | 6 |  |  |
Real estate investments | 5 |  | — |  | — |  | 21 |  | 26 |  | 12 |  | 14 |
Special situations | — |  | — |  | — |  | 3 |  | 3 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 22 |  | 22 |  | 9 |  | 12 |
Private credit | — |  | — |  | — |  | — |  | — |  | 3 |  | — |
Infrastructure | — |  | — |  | — |  | — |  | — |  | 2 |  | — |
Total | $ | 59 |  | $ | 82 |  | $ | — |  | $ | 46 |  | $ | 187 |  | 100% | 100 | %
Southern Company Gas |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 41 | % | 40 | %
Domestic equity | $ | 130 |  | $ | 52 |  | $ | — |  | $ | — |  | $ | 182 |  |  |
International equity | 130 |  | 71 |  | — |  | — |  | 201 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 32 |
U.S. Treasury, government, and agency bonds | — |  | 132 |  | — |  | — |  | 132 |  |  |
Mortgage- and asset-backed securities | — |  | 3 |  | — |  | — |  | 3 |  |  |
Corporate bonds | — |  | 116 |  | — |  | — |  | 116 |  |  |
Pooled funds | — |  | 52 |  | — |  | — |  | 52 |  |  |
Cash equivalents and other | 25 |  | 4 |  | — |  | — |  | 29 |  |  |
Real estate investments | 25 |  | — |  | — |  | 113 |  | 138 |  | 12 |  | 14 |
Special situations | — |  | — |  | — |  | 16 |  | 16 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 118 |  | 118 |  | 9 |  | 12 |
Private credit | — |  | — |  | — |  | 2 |  | 2 |  | 3 |  | — |
Infrastructure | — |  | — |  | — |  | — |  | — |  | 2 |  | — |
Total | $ | 310 |  | $ | 430 |  | $ | — |  | $ | 249 |  | $ | 989 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs | Significant Unobservable Inputs | Net Asset Value as a Practical Expedient |  | Target Allocation | Actual Allocation
At December 31, 2022: | (Level 1) | (Level 2) | (Level 3) | (NAV) | Total
| (in millions) |  |
Southern Company |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 45 | % | 43 | %
Domestic equity | $ | 2,078 |  | $ | 691 |  | $ | — |  | $ | — |  | $ | 2,769 |  |  |
International equity | 2,166 |  | 1,090 |  | — |  | — |  | 3,256 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 28 |
U.S. Treasury, government, and agency bonds | — |  | 1,469 |  | — |  | — |  | 1,469 |  |  |
Mortgage- and asset-backed securities | — |  | 29 |  | — |  | — |  | 29 |  |  |
Corporate bonds | — |  | 1,494 |  | — |  | — |  | 1,494 |  |  |
Pooled funds | — |  | 607 |  | — |  | — |  | 607 |  |  |
Cash equivalents and other | 399 |  | 7 |  | — |  | — |  | 406 |  |  |
Real estate investments | 376 |  | — |  | — |  | 1,887 |  | 2,263 |  | 13 |  | 15 |
Special situations | — |  | — |  | — |  | 187 |  | 187 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 1,717 |  | 1,717 |  | 9 |  | 12 |
Total | $ | 5,019 |  | $ | 5,387 |  | $ | — |  | $ | 3,791 |  | $ | 14,197 |  | 100 | % | 100 | %
Liabilities: |  |  |  |  |  |  |
Derivatives | (4) |  | — |  | — |  | — |  | (4) |  |  |
Total | $ | 5,015 |  | $ | 5,387 |  | $ | — |  | $ | 3,791 |  | $ | 14,193 |  | 100 | % | 100 | %
Alabama Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 45 | % | 43 | %
Domestic equity | $ | 500 |  | $ | 167 |  | $ | — |  | $ | — |  | $ | 667 |  |  |
International equity | 522 |  | 263 |  | — |  | — |  | 785 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 28 |
U.S. Treasury, government, and agency bonds | — |  | 354 |  | — |  | — |  | 354 |  |  |
Mortgage- and asset-backed securities | — |  | 7 |  | — |  | — |  | 7 |  |  |
Corporate bonds | — |  | 360 |  | — |  | — |  | 360 |  |  |
Pooled funds | — |  | 146 |  | — |  | — |  | 146 |  |  |
Cash equivalents and other | 96 |  | 2 |  | — |  | — |  | 98 |  |  |
Real estate investments | 91 |  | — |  | — |  | 455 |  | 546 |  | 13 |  | 15 |
Special situations | — |  | — |  | — |  | 45 |  | 45 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 414 |  | 414 |  | 9 |  | 12 |
Total | $ | 1,209 |  | $ | 1,299 |  | $ | — |  | $ | 914 |  | $ | 3,422 |  | 100 | % | 100 | %
Liabilities: |  |  |  |  |  |  |
Derivatives | (1) |  | — |  | — |  | — |  | (1) |  |  |
Total | $ | 1,208 |  | $ | 1,299 |  | $ | — |  | $ | 914 |  | $ | 3,421 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs | Significant Unobservable Inputs | Net Asset Value as a Practical Expedient |  | Target Allocation | Actual Allocation
At December 31, 2022: | (Level 1) | (Level 2) | (Level 3) | (NAV) | Total
| (in millions) |  |
Georgia Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 45 | % | 43 | %
Domestic equity | $ | 651 |  | $ | 217 |  | $ | — |  | $ | — |  | $ | 868 |  |  |
International equity | 678 |  | 342 |  | — |  | — |  | 1,020 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 28 |
U.S. Treasury, government, and agency bonds | — |  | 460 |  | — |  | — |  | 460 |  |  |
Mortgage- and asset-backed securities | — |  | 9 |  | — |  | — |  | 9 |  |  |
Corporate bonds | — |  | 468 |  | — |  | — |  | 468 |  |  |
Pooled funds | — |  | 190 |  | — |  | — |  | 190 |  |  |
Cash equivalents and other | 125 |  | 2 |  | — |  | — |  | 127 |  |  |
Real estate investments | 118 |  | — |  | — |  | 591 |  | 709 |  | 13 |  | 15 |
Special situations | — |  | — |  | — |  | 59 |  | 59 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 538 |  | 538 |  | 9 |  | 12 |
Total | $ | 1,572 |  | $ | 1,688 |  | $ | — |  | $ | 1,188 |  | $ | 4,448 |  | 100 | % | 100 | %
Liabilities: |  |  |  |  |  |  |
Derivatives | (1) |  | — |  | — |  | — |  | (1) |  |  |
Total | $ | 1,571 |  | $ | 1,688 |  | $ | — |  | $ | 1,188 |  | $ | 4,447 |  | 100 | % | 100 | %
Mississippi Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 45 | % | 43 | %
Domestic equity | $ | 95 |  | $ | 32 |  | $ | — |  | $ | — |  | $ | 127 |  |  |
International equity | 99 |  | 50 |  | — |  | — |  | 149 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 28 |
U.S. Treasury, government, and agency bonds | — |  | 67 |  | — |  | — |  | 67 |  |  |
Mortgage- and asset-backed securities | — |  | 1 |  | — |  | — |  | 1 |  |  |
Corporate bonds | — |  | 68 |  | — |  | — |  | 68 |  |  |
Pooled funds | — |  | 28 |  | — |  | — |  | 28 |  |  |
Cash equivalents and other | 18 |  | — |  | — |  | — |  | 18 |  |  |
Real estate investments | 17 |  | — |  | — |  | 86 |  | 103 |  | 13 |  | 15 |
Special situations | — |  | — |  | — |  | 9 |  | 9 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 78 |  | 78 |  | 9 |  | 12 |
Total | $ | 229 |  | $ | 246 |  | $ | — |  | $ | 173 |  | $ | 648 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs | Significant Unobservable Inputs | Net Asset Value as a Practical Expedient |  | Target Allocation | Actual Allocation
At December 31, 2022: | (Level 1) | (Level 2) | (Level 3) | (NAV) | Total
| (in millions) |  |
Southern Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 45 | % | 43 | %
Domestic equity | $ | 25 |  | $ | 9 |  | $ | — |  | $ | — |  | $ | 34 |  |  |
International equity | 27 |  | 14 |  | — |  | — |  | 41 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 28 |
U.S. Treasury, government, and agency bonds | — |  | 18 |  | — |  | — |  | 18 |  |  |
Corporate bonds | — |  | 19 |  | — |  | — |  | 19 |  |  |
Pooled funds | — |  | 8 |  | — |  | — |  | 8 |  |  |
Cash equivalents and other | 5 |  | — |  | — |  | — |  | 5 |  |  |
Real estate investments | 5 |  | — |  | — |  | 24 |  | 29 |  | 13 |  | 15 |
Special situations | — |  | — |  | — |  | 2 |  | 2 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 21 |  | 21 |  | 9 |  | 12 |
Total | $ | 62 |  | $ | 68 |  | $ | — |  | $ | 47 |  | $ | 177 |  | 100 | % | 100 | %
Southern Company Gas |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 45 | % | 43 | %
Domestic equity | $ | 146 |  | $ | 49 |  | $ | — |  | $ | — |  | $ | 195 |  |  |
International equity | 152 |  | 77 |  | — |  | — |  | 229 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 28 |
U.S. Treasury, government, and agency bonds | — |  | 104 |  | — |  | — |  | 104 |  |  |
Mortgage- and asset-backed securities | — |  | 2 |  | — |  | — |  | 2 |  |  |
Corporate bonds | — |  | 105 |  | — |  | — |  | 105 |  |  |
Pooled funds | — |  | 43 |  | — |  | — |  | 43 |  |  |
Cash equivalents and other | 28 |  | 1 |  | — |  | — |  | 29 |  |  |
Real estate investments | 27 |  | — |  | — |  | 133 |  | 160 |  | 13 |  | 15 |
Special situations | — |  | — |  | — |  | 13 |  | 13 |  | 3 |  | 2 |
Private equity | — |  | — |  | — |  | 121 |  | 121 |  | 9 |  | 12 |
Total | $ | 353 |  | $ | 381 |  | $ | — |  | $ | 267 |  | $ | 1,001 |  | 100 | % | 100 | %
The fair values, and actual allocations relative to the target allocations, of the applicable Registrants' other postretirement benefit plan assets at December 31, 2023 and 2022 are presented below.
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs |  | Net Asset Value as a Practical Expedient | Total | Target Allocation | Actual Allocation
At December 31, 2023: | (Level 1) | (Level 2) |  | (NAV)
| (in millions) |  |
Southern Company |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 60 | % | 61 | %
Domestic equity | $ | 85 |  | $ | 87 |  |  | $ | — |  | $ | 172 |  |  |
International equity | 53 |  | 82 |  |  | — |  | 135 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 28 |
U.S. Treasury, government, and agency bonds | — |  | 57 |  |  | — |  | 57 |  |  |
Mortgage- and asset-backed securities | — |  | 2 |  |  | — |  | 2 |  |  |
Corporate bonds | — |  | 47 |  |  | — |  | 47 |  |  |
Pooled funds | — |  | 92 |  |  | — |  | 92 |  |  |
Cash equivalents and other | 21 |  | 2 |  |  | — |  | 23 |  |  |
Trust-owned life insurance | — |  | 456 |  |  | — |  | 456 |  |  |
Real estate investments | 11 |  | — |  |  | 46 |  | 57 |  | 4 |  | 6 |
Special situations | — |  | — |  |  | 6 |  | 6 |  | 1 |  | 1 |
Private equity | — |  | — |  |  | 48 |  | 48 |  | 3 |  | 4 |
Private credit | — |  | — |  |  | 1 |  | 1 |  | 1 |  | — |
Infrastructure | — |  | — |  |  | — |  | — |  | 1 |  | — |
Total | $ | 170 |  | $ | 825 |  |  | $ | 101 |  | $ | 1,096 |  | 100 | % | 100 | %
Alabama Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 67 | % | 66 | %
Domestic equity | $ | 16 |  | $ | 6 |  |  | $ | — |  | $ | 22 |  |  |
International equity | 16 |  | 9 |  |  | — |  | 25 |  |  |
Fixed income: |  |  |  |  |  | 23 |  | 23 |
U.S. Treasury, government, and agency bonds | — |  | 16 |  |  | — |  | 16 |  |  |
Corporate bonds | — |  | 14 |  |  | — |  | 14 |  |  |
Pooled funds | — |  | 8 |  |  | — |  | 8 |  |  |
Cash equivalents and other | 3 |  | — |  |  | — |  | 3 |  |  |
Trust-owned life insurance | — |  | 280 |  |  | — |  | 280 |  |  |
Real estate investments | 3 |  | — |  |  | 14 |  | 17 |  | 4 |  | 6 |
Special situations | — |  | — |  |  | 2 |  | 2 |  | 1 |  | 1 |
Private equity | — |  | — |  |  | 15 |  | 15 |  | 3 |  | 4 |
Private credit | — |  | — |  |  | — |  | — |  | 1 |  | — |
Infrastructure | — |  | — |  |  | — |  | — |  | 1 |  | — |
Total | $ | 38 |  | $ | 333 |  |  | $ | 31 |  | $ | 402 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs |  | Net Asset Value as a Practical Expedient | Total | Target Allocation | Actual Allocation
At December 31, 2023: | (Level 1) | (Level 2) |  | (NAV)
| (in millions) |  |
Georgia Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 58 | % | 57 | %
Domestic equity | $ | 47 |  | $ | 6 |  |  | $ | — |  | $ | 53 |  |  |
International equity | 16 |  | 40 |  |  | — |  | 56 |  |  |
Fixed income: |  |  |  |  |  | 35 |  | 35 |
U.S. Treasury, government, and agency bonds | — |  | 16 |  |  | — |  | 16 |  |  |
Corporate bonds | — |  | 14 |  |  | — |  | 14 |  |  |
Pooled funds | — |  | 47 |  |  | — |  | 47 |  |  |
Cash equivalents and other | 13 |  | — |  |  | — |  | 13 |  |  |
Trust-owned life insurance | — |  | 176 |  |  | — |  | 176 |  |  |
Real estate investments | 4 |  | — |  |  | 14 |  | 18 |  | 3 |  | 4 |
Special situations | — |  | — |  |  | 2 |  | 2 |  | 1 |  | 1 |
Private equity | — |  | — |  |  | 14 |  | 14 |  | 2 |  | 3 |
Private credit | — |  | — |  |  | — |  | — |  | 1 |  | — |
Infrastructure | — |  | — |  |  | — |  | — |  | — |  | — |
Total | $ | 80 |  | $ | 299 |  |  | $ | 30 |  | $ | 409 |  | 100 | % | 100 | %
Mississippi Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 34 | % | 33 | %
Domestic equity | $ | 3 |  | $ | 1 |  |  | $ | — |  | $ | 4 |  |  |
International equity | 3 |  | 1 |  |  | — |  | 4 |  |  |
Fixed income: |  |  |  |  |  | 43 |  | 44 |
U.S. Treasury, government, and agency bonds | — |  | 7 |  |  | — |  | 7 |  |  |
Corporate bonds | — |  | 2 |  |  | — |  | 2 |  |  |
Pooled funds | — |  | 1 |  |  | — |  | 1 |  |  |
Cash equivalents and other | 1 |  | — |  |  | — |  | 1 |  |  |
Real estate investments | 1 |  | — |  |  | 2 |  | 3 |  | 10 |  | 11 |
Special situations | — |  | — |  |  | — |  | — |  | 2 |  | 2 |
Private equity | — |  | — |  |  | 2 |  | 2 |  | 7 |  | 10 |
Private credit | — |  | — |  |  | — |  | — |  | 3 |  | — |
Infrastructure | — |  | — |  |  | — |  | — |  | 1 |  | — |
Total | $ | 8 |  | $ | 12 |  |  | $ | 4 |  | $ | 24 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs |  | Net Asset Value as a Practical Expedient | Total | Target Allocation | Actual Allocation
At December 31, 2023: | (Level 1) | (Level 2) |  | (NAV)
| (in millions) |  |
Southern Company Gas |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 72 | % | 72 | %
Domestic equity | $ | 2 |  | $ | 67 |  |  | $ | — |  | $ | 69 |  |  |
International equity | 2 |  | 22 |  |  | — |  | 24 |  |  |
Fixed income: |  |  |  |  |  | 26 |  | 26 |
U.S. Treasury, government, and agency bonds | — |  | 1 |  |  | — |  | 1 |  |  |
Corporate bonds | — |  | 1 |  |  | — |  | 1 |  |  |
Pooled funds | — |  | 29 |  |  | — |  | 29 |  |  |
Cash equivalents and other | 1 |  | — |  |  | — |  | 1 |  |  |
Trust-owned life insurance | — |  | — |  |  | — |  | — |  |  |
Real estate investments | — |  | — |  |  | 1 |  | 1 |  | 1 |  | 1 |
Private equity | — |  | — |  |  | 1 |  | 1 |  | 1 |  | 1 |
Total | $ | 5 |  | $ | 120 |  |  | $ | 2 |  | $ | 127 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs |  | Net Asset Value as a Practical Expedient |  | Target Allocation | Actual Allocation
At December 31, 2022: | (Level 1) | (Level 2) |  | (NAV) | Total
| (in millions) |  |
Southern Company |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 61 | % | 59 | %
Domestic equity | $ | 85 |  | $ | 74 |  |  | $ | — |  | $ | 159 |  |  |
International equity | 58 |  | 79 |  |  | — |  | 137 |  |  |
Fixed income: |  |  |  |  |  | 30 |  | 28 |
U.S. Treasury, government, and agency bonds | — |  | 43 |  |  | — |  | 43 |  |  |
Mortgage- and asset-backed securities | — |  | 1 |  |  | — |  | 1 |  |  |
Corporate bonds | — |  | 40 |  |  | — |  | 40 |  |  |
Pooled funds | — |  | 79 |  |  | — |  | 79 |  |  |
Cash equivalents and other | 19 |  | — |  |  | — |  | 19 |  |  |
Trust-owned life insurance | — |  | 406 |  |  | — |  | 406 |  |  |
Real estate investments | 11 |  | — |  |  | 51 |  | 62 |  | 5 |  | 7 |
Special situations | — |  | — |  |  | 6 |  | 6 |  | 1 |  | 1 |
Private equity | — |  | — |  |  | 46 |  | 46 |  | 3 |  | 5 |
Total | $ | 173 |  | $ | 722 |  |  | $ | 103 |  | $ | 998 |  | 100 | % | 100 | %
Alabama Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 69 | % | 65 | %
Domestic equity | $ | 17 |  | $ | 6 |  |  | $ | — |  | $ | 23 |  |  |
International equity | 18 |  | 9 |  |  | — |  | 27 |  |  |
Fixed income: |  |  |  |  |  | 23 |  | 23 |
U.S. Treasury, government, and agency bonds | — |  | 12 |  |  | — |  | 12 |  |  |
Corporate bonds | — |  | 12 |  |  | — |  | 12 |  |  |
Pooled funds | — |  | 7 |  |  | — |  | 7 |  |  |
Cash equivalents and other | 3 |  | — |  |  | — |  | 3 |  |  |
Trust-owned life insurance | — |  | 252 |  |  | — |  | 252 |  |  |
Real estate investments | 3 |  | — |  |  | 16 |  | 19 |  | 4 |  | 7 |
Special situations | — |  | — |  |  | 2 |  | 2 |  | 1 |  | 1 |
Private equity | — |  | — |  |  | 14 |  | 14 |  | 3 |  | 4 |
Total | $ | 41 |  | $ | 298 |  |  | $ | 32 |  | $ | 371 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs |  | Net Asset Value as a Practical Expedient |  | Target Allocation | Actual Allocation
At December 31, 2022: | (Level 1) | (Level 2) |  | (NAV) | Total
| (in millions) |  |
Georgia Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 58 | % | 56 | %
Domestic equity | $ | 46 |  | $ | 6 |  |  | $ | — |  | $ | 52 |  |  |
International equity | 17 |  | 39 |  |  | — |  | 56 |  |  |
Fixed income: |  |  |  |  |  | 35 |  | 34 |
U.S. Treasury, government, and agency bonds | — |  | 10 |  |  | — |  | 10 |  |  |
Corporate bonds | — |  | 12 |  |  | — |  | 12 |  |  |
Pooled funds | — |  | 40 |  |  | — |  | 40 |  |  |
Cash equivalents and other | 9 |  | — |  |  | — |  | 9 |  |  |
Trust-owned life insurance | — |  | 154 |  |  | — |  | 154 |  |  |
Real estate investments | 4 |  | — |  |  | 15 |  | 19 |  | 4 |  | 5 |
Special situations | — |  | — |  |  | 2 |  | 2 |  | 1 |  | 1 |
Private equity | — |  | — |  |  | 14 |  | 14 |  | 2 |  | 4 |
Total | $ | 76 |  | $ | 261 |  |  | $ | 31 |  | $ | 368 |  | 100 | % | 100 | %
Mississippi Power |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 37 | % | 35 | %
Domestic equity | $ | 3 |  | $ | 1 |  |  | $ | — |  | $ | 4 |  |  |
International equity | 3 |  | 2 |  |  | — |  | 5 |  |  |
Fixed income: |  |  |  |  |  | 43 |  | 41 |
U.S. Treasury, government, and agency bonds | — |  | 4 |  |  | — |  | 4 |  |  |
Corporate bonds | — |  | 2 |  |  | — |  | 2 |  |  |
Pooled funds | — |  | 1 |  |  | — |  | 1 |  |  |
Cash equivalents and other | 2 |  | — |  |  | — |  | 2 |  |  |
Real estate investments | 1 |  | — |  |  | 3 |  | 4 |  | 11 |  | 12 |
Special situations | — |  | — |  |  | — |  | — |  | 2 |  | 2 |
Private equity | — |  | — |  |  | 2 |  | 2 |  | 7 |  | 10 |
Total | $ | 9 |  | $ | 10 |  |  | $ | 5 |  | $ | 24 |  | 100 | % | 100 | %
| Fair Value Measurements Using |  |  |
| Quoted Prices in Active Markets for Identical Assets | Significant Other Observable Inputs |  | Net Asset Value as a Practical Expedient |  | Target Allocation | Actual Allocation
At December 31, 2022: | (Level 1) | (Level 2) |  | (NAV) | Total
| (in millions) |  |
Southern Company Gas |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Equity: |  |  |  |  |  | 72 | % | 70 | %
Domestic equity | $ | 2 |  | $ | 56 |  |  | $ | — |  | $ | 58 |  |  |
International equity | 2 |  | 20 |  |  | — |  | 22 |  |  |
Fixed income: |  |  |  |  |  | 26 |  | 27 |
U.S. Treasury, government, and agency bonds | — |  | 1 |  |  | — |  | 1 |  |  |
Corporate bonds | — |  | 1 |  |  | — |  | 1 |  |  |
Pooled funds | — |  | 27 |  |  | — |  | 27 |  |  |
Cash equivalents and other | 1 |  | — |  |  | — |  | 1 |  |  |
Real estate investments | — |  | — |  |  | 2 |  | 2 |  | 1 |  | 2 |
Private equity | — |  | — |  |  | 1 |  | 1 |  | 1 |  | 1 |
Total | $ | 5 |  | $ | 105 |  |  | $ | 3 |  | $ | 113 |  | 100 | % | 100 | %
Total matching contributions | Total matching contributions made to the plans for 2023, 2022, and 2021 were as follows:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
2023 | $ | 131 |  | $ | 28 |  | $ | 31 |  | $ | 5 |  | $ | 3 |  | $ | 18 |
2022 | 124 |  | 26 |  | 29 |  | 5 |  | 3 |  | 17 |
2021 | 119 |  | 26 |  | 28 |  | 5 |  | 2 |  | 16 |

X
- Definition Components of other comprehensive income along with changes in balances of regulatory assets and regulatory liabilities related to defined benefit pension plans. + References No definition available. + Details
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X
- Definition Tabular disclosure of defined benefit plan asset investment. Includes, but is not limited to, fair value of category of plan asset and its level within fair value hierarchy. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of defined contribution pension plans or defined contribution other postretirement plans, separately for pension plans and other postretirement benefit plans. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480794/715-70-50-1 + Details
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- Definition Tabular disclosure of benefit obligations including accumulated benefit obligation and projected benefit obligation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (e) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of benefit obligation and plan assets of defined benefit plan with accumulated benefit obligation in excess of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-3 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-3 + Details
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- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (d)(5) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of the amounts that are recognized in the balance sheet (or statement of financial position) for pension plans and/or other employee benefit plans, showing separately the assets and current and noncurrent liabilities (if applicable) recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of the net gain (loss) and net prior service cost or credit recognized in other comprehensive income (loss) for the period for pension plans and/or other employee benefit plans, and reclassification adjustments of other comprehensive income (loss) for the period, as those amounts, including amortization of the net transition asset or obligation, are recognized as components of net periodic benefit cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (i) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of assumption used to determine benefit obligation and net periodic benefit cost of defined benefit plan. Includes, but is not limited to, discount rate, rate of compensation increase, expected long-term rate of return on plan assets and interest crediting rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of benefit obligation and plan assets for defined benefit pension plan with projected benefit obligation in excess of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-3 + Details
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- Definition Tabular disclosure of the changes in plan assets and benefit obligations recognized in other comprehensive income (loss) during the period. + References No definition available. + Details
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- Definition Tabular disclosure of benefits expected to be paid by pension plans and/or other employee benefit plans in each of the next five fiscal years and in the aggregate for the five fiscal years thereafter. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (f) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of the assumed health care cost trend rates for the next year used to measure the expected cost of benefits covered by the plans, including the ultimate trend rate(s) and when that rate is expected to be achieved. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (l) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (h) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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