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FAIR VALUE MEASUREMENTS (Tables) | 12 Months Ended
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Dec. 31, 2023
Fair Value Disclosures [Abstract] |
Assets and liabilities measured at fair value on a recurring basis | The fair value increases (decreases) of the Funds, including unrealized gains (losses) and reinvested interest and dividends and excluding the Funds' expenses, for 2023, 2022, and 2021 are shown in the table below.
| Southern Company | Alabama Power | Georgia Power
| (in millions)
Fair value increases (decreases) |  |  |
2023 | $ | 281 |  | $ | 157 |  | $ | 124 |
2022 | (360) |  | (171) |  | (189) |
2021 | 274 |  | 200 |  | 74 |
Unrealized gains (losses) |  |  |
At December 31, 2023 | $ | 241 |  | $ | 119 |  | $ | 122 |
At December 31, 2022 | (391) |  | (204) |  | (187) |
At December 31, 2021 | (27) |  | (30) |  | 3 |
At December 31, 2023, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:
| 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 |  |
At December 31, 2023: | (Level 1) |  | (Level 2) |  | (Level 3) |  | (NAV) |  | Total
| (in millions)
Southern Company |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives(a) | $ | 6 |  |  | $ | 49 |  |  | $ | — |  |  | $ | — |  |  | $ | 55 |
Investments in trusts:(b) |  |  |  |  |  |  |  |  |
Domestic equity | 764 |  |  | 216 |  |  | — |  |  | — |  |  | 980 |
Foreign equity | 145 |  |  | 171 |  |  | — |  |  | — |  |  | 316 |
U.S. Treasury and government agency securities | — |  |  | 369 |  |  | — |  |  | — |  |  | 369 |
Municipal bonds | — |  |  | 48 |  |  | — |  |  | — |  |  | 48 |
Pooled funds – fixed income | — |  |  | 6 |  |  | — |  |  | — |  |  | 6 |
Corporate bonds | — |  |  | 389 |  |  | — |  |  | — |  |  | 389 |
Mortgage and asset backed securities | — |  |  | 89 |  |  | — |  |  | — |  |  | 89 |
Private equity | — |  |  | — |  |  | — |  |  | 169 |  |  | 169 |
Cash and cash equivalents | 3 |  |  | — |  |  | — |  |  | — |  |  | 3 |
Other | 58 |  |  | 3 |  |  | — |  |  | 9 |  |  | 70 |
Cash equivalents and restricted cash | 253 |  |  | 15 |  |  | — |  |  | — |  |  | 268 |
Other investments | 9 |  |  | 27 |  |  | 8 |  |  | — |  |  | 44 |
Total | $ | 1,238 |  |  | $ | 1,382 |  |  | $ | 8 |  |  | $ | 178 |  |  | $ | 2,806 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives(a) | $ | 46 |  |  | $ | 312 |  |  | $ | — |  |  | $ | — |  |  | $ | 358 |
Interest rate derivatives | — |  |  | 264 |  |  | — |  |  | — |  |  | 264 |
Foreign currency derivatives | — |  |  | 122 |  |  | — |  |  | — |  |  | 122 |
Contingent consideration | 3 |  |  | — |  |  | 16 |  |  | — |  |  | 19 |
Other | — |  |  | 13 |  |  | — |  |  | — |  |  | 13 |
Total | $ | 49 |  |  | $ | 711 |  |  | $ | 16 |  |  | $ | — |  |  | $ | 776 |
| 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 |  |
At December 31, 2023: | (Level 1) |  | (Level 2) |  | (Level 3) |  | (NAV) |  | Total
| (in millions)
Alabama Power |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 15 |  |  | $ | — |  |  | $ | — |  |  | $ | 15 |
Nuclear decommissioning trusts:(b) |  |  |  |  |  |  |  |  |
Domestic equity | 443 |  |  | 208 |  |  | — |  |  | — |  |  | 651 |
Foreign equity | 145 |  |  | — |  |  | — |  |  | — |  |  | 145 |
U.S. Treasury and government agency securities | — |  |  | 20 |  |  | — |  |  | — |  |  | 20 |
Municipal bonds | — |  |  | 1 |  |  | — |  |  | — |  |  | 1 |
Corporate bonds | — |  |  | 231 |  |  | — |  |  | — |  |  | 231 |
Mortgage and asset backed securities | — |  |  | 25 |  |  | — |  |  | — |  |  | 25 |
Private equity | — |  |  | — |  |  | — |  |  | 169 |  |  | 169 |
Other | 8 |  |  | — |  |  | — |  |  | 9 |  |  | 17 |
Cash equivalents and restricted cash | 119 |  |  | 15 |  |  | — |  |  | — |  |  | 134 |
Other investments | — |  |  | 27 |  |  | — |  |  | — |  |  | 27 |
Total | $ | 715 |  |  | $ | 542 |  |  | $ | — |  |  | $ | 178 |  |  | $ | 1,435 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 110 |  |  | $ | — |  |  | $ | — |  |  | $ | 110 |
Georgia Power |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 13 |  |  | $ | — |  |  | $ | — |  |  | $ | 13 |
Nuclear decommissioning trusts:(b) |  |  |  |  |  |  |  |  |
Domestic equity | 321 |  |  | 1 |  |  | — |  |  | — |  |  | 322 |
Foreign equity | — |  |  | 170 |  |  | — |  |  | — |  |  | 170 |
U.S. Treasury and government agency securities | — |  |  | 349 |  |  | — |  |  | — |  |  | 349 |
Municipal bonds | — |  |  | 47 |  |  | — |  |  | — |  |  | 47 |
Corporate bonds | — |  |  | 158 |  |  | — |  |  | — |  |  | 158 |
Mortgage and asset backed securities | — |  |  | 64 |  |  | — |  |  | — |  |  | 64 |
Other | 50 |  |  | 3 |  |  | — |  |  | — |  |  | 53 |
Total | $ | 371 |  |  | $ | 805 |  |  | $ | — |  |  | $ | — |  |  | $ | 1,176 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 124 |  |  | $ | — |  |  | $ | — |  |  | $ | 124 |
| 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 |  |
At December 31, 2023: | (Level 1) |  | (Level 2) |  | (Level 3) |  | (NAV) |  | Total
| (in millions)
Mississippi Power |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 15 |  |  | $ | — |  |  | $ | — |  |  | $ | 15 |
Cash equivalents | 17 |  |  | — |  |  | — |  |  | — |  |  | 17 |
Total | $ | 17 |  |  | $ | 15 |  |  | $ | — |  |  | $ | — |  |  | $ | 32 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 61 |  |  | $ | — |  |  | $ | — |  |  | $ | 61 |
Southern Power |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 3 |  |  | $ | — |  |  | $ | — |  |  | $ | 3 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 5 |  |  | $ | — |  |  | $ | — |  |  | $ | 5 |
Foreign currency derivatives | — |  |  | 22 |  |  | — |  |  | — |  |  | 22 |
Contingent consideration | 3 |  |  | — |  |  | 16 |  |  | — |  |  | 19 |
Other | — |  |  | 13 |  |  | — |  |  | — |  |  | 13 |
Total | $ | 3 |  |  | $ | 40 |  |  | $ | 16 |  |  | $ | — |  |  | $ | 59 |
Southern Company Gas |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives(a) | $ | 6 |  |  | $ | 3 |  |  | $ | — |  |  | $ | — |  |  | $ | 9 |
Non-qualified deferred compensation trusts: |  |  |  |  |  |  |  |  |
Domestic equity | — |  |  | 7 |  |  | — |  |  | — |  |  | 7 |
Foreign equity | — |  |  | 1 |  |  | — |  |  | — |  |  | 1 |
Pooled funds - fixed income | — |  |  | 6 |  |  | — |  |  | — |  |  | 6 |
Cash and cash equivalents | 3 |  |  | — |  |  | — |  |  | — |  |  | 3 |
Total | $ | 9 |  |  | $ | 17 |  |  | $ | — |  |  | $ | — |  |  | $ | 26 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives(a)(b) | $ | 46 |  |  | $ | 12 |  |  | $ | — |  |  | $ | — |  |  | $ | 58 |
Interest rate derivatives | — |  |  | 79 |  |  | — |  |  | — |  |  | 79 |
Total | $ | 46 |  |  | $ | 91 |  |  | $ | — |  |  | $ | — |  |  | $ | 137 |
(a)Excludes cash collateral of $62 million. (b)Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 under "Nuclear Decommissioning" for additional information. At December 31, 2022, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:
| 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 |  |
At December 31, 2022: | (Level 1) |  | (Level 2) |  | (Level 3) |  | (NAV) |  | Total
| (in millions)
Southern Company |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives(a) | $ | 18 |  |  | $ | 181 |  |  | $ | — |  |  | $ | — |  |  | $ | 199 |
Interest rate derivatives | — |  |  | 12 |  |  | — |  |  | — |  |  | 12 |
Investments in trusts:(b)(c) |  |  |  |  |  |  |  |  |
Domestic equity | 651 |  |  | 178 |  |  | — |  |  | — |  |  | 829 |
Foreign equity | 125 |  |  | 150 |  |  | — |  |  | — |  |  | 275 |
U.S. Treasury and government agency securities | — |  |  | 285 |  |  | — |  |  | — |  |  | 285 |
Municipal bonds | — |  |  | 51 |  |  | — |  |  | — |  |  | 51 |
Pooled funds – fixed income | — |  |  | 7 |  |  | — |  |  | — |  |  | 7 |
Corporate bonds | — |  |  | 412 |  |  | — |  |  | — |  |  | 412 |
Mortgage and asset backed securities | — |  |  | 90 |  |  | — |  |  | — |  |  | 90 |
Private equity | — |  |  | — |  |  | — |  |  | 161 |  |  | 161 |
Cash and cash equivalents | 4 |  |  | — |  |  | — |  |  | — |  |  | 4 |
Other | 37 |  |  | 12 |  |  | — |  |  | — |  |  | 49 |
Cash equivalents | 1,427 |  |  | 20 |  |  | — |  |  | — |  |  | 1,447 |
Other investments | 9 |  |  | 26 |  |  | — |  |  | — |  |  | 35 |
Total | $ | 2,271 |  |  | $ | 1,424 |  |  | $ | — |  |  | $ | 161 |  |  | $ | 3,856 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives(a) | $ | 32 |  |  | $ | 178 |  |  | $ | — |  |  | $ | — |  |  | $ | 210 |
Interest rate derivatives | — |  |  | 302 |  |  | — |  |  | — |  |  | 302 |
Foreign currency derivatives | — |  |  | 216 |  |  | — |  |  | — |  |  | 216 |
Contingent consideration | — |  |  | — |  |  | 12 |  |  | — |  |  | 12 |
Other | — |  |  | 13 |  |  | — |  |  | — |  |  | 13 |
Total | $ | 32 |  |  | $ | 709 |  |  | $ | 12 |  |  | $ | — |  |  | $ | 753 |
| 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 |  |
At December 31, 2022: | (Level 1) |  | (Level 2) |  | (Level 3) |  | (NAV) |  | Total
| (in millions)
Alabama Power |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 62 |  |  | $ | — |  |  | $ | — |  |  | $ | 62 |
Nuclear decommissioning trusts:(b) |  |  |  |  |  |  |  |  |
Domestic equity | 396 |  |  | 169 |  |  | — |  |  | — |  |  | 565 |
Foreign equity | 125 |  |  | — |  |  | — |  |  | — |  |  | 125 |
U.S. Treasury and government agency securities | — |  |  | 19 |  |  | — |  |  | — |  |  | 19 |
Municipal bonds | — |  |  | 1 |  |  | — |  |  | — |  |  | 1 |
Corporate bonds | — |  |  | 225 |  |  | — |  |  | — |  |  | 225 |
Mortgage and asset backed securities | — |  |  | 22 |  |  | — |  |  | — |  |  | 22 |
Private equity | — |  |  | — |  |  | — |  |  | 161 |  |  | 161 |
Other | 7 |  |  | — |  |  | — |  |  | — |  |  | 7 |
Cash equivalents | 438 |  |  | 20 |  |  | — |  |  | — |  |  | 458 |
Other investments | — |  |  | 26 |  |  | — |  |  | — |  |  | 26 |
Total | $ | 966 |  |  | $ | 544 |  |  | $ | — |  |  | $ | 161 |  |  | $ | 1,671 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 39 |  |  | $ | — |  |  | $ | — |  |  | $ | 39 |
Georgia Power |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 42 |  |  | $ | — |  |  | $ | — |  |  | $ | 42 |
Nuclear decommissioning trusts:(b)(c) |  |  |  |  |  |  |  |  |
Domestic equity | 255 |  |  | 1 |  |  | — |  |  | — |  |  | 256 |
Foreign equity | — |  |  | 149 |  |  | — |  |  | — |  |  | 149 |
U.S. Treasury and government agency securities | — |  |  | 266 |  |  | — |  |  | — |  |  | 266 |
Municipal bonds | — |  |  | 50 |  |  | — |  |  | — |  |  | 50 |
Corporate bonds | — |  |  | 187 |  |  | — |  |  | — |  |  | 187 |
Mortgage and asset backed securities | — |  |  | 68 |  |  | — |  |  | — |  |  | 68 |
Other | 30 |  |  | 12 |  |  | — |  |  | — |  |  | 42 |
Cash equivalents | 355 |  |  | — |  |  | — |  |  | — |  |  | 355 |
Total | $ | 640 |  |  | $ | 775 |  |  | $ | — |  |  | $ | — |  |  | $ | 1,415 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 62 |  |  | $ | — |  |  | $ | — |  |  | $ | 62 |
| 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 |  |
At December 31, 2022: | (Level 1) |  | (Level 2) |  | (Level 3) |  | (NAV) |  | Total
| (in millions)
Mississippi Power |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 59 |  |  | $ | — |  |  | $ | — |  |  | $ | 59 |
Cash equivalents | 47 |  |  | — |  |  | — |  |  | — |  |  | 47 |
Total | $ | 47 |  |  | $ | 59 |  |  | $ | — |  |  | $ | — |  |  | $ | 106 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 32 |  |  | $ | — |  |  | $ | — |  |  | $ | 32 |
Southern Power |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 8 |  |  | $ | — |  |  | $ | — |  |  | $ | 8 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives | $ | — |  |  | $ | 12 |  |  | $ | — |  |  | $ | — |  |  | $ | 12 |
Foreign currency derivatives | — |  |  | 47 |  |  | — |  |  | — |  |  | 47 |
Contingent consideration | — |  |  | — |  |  | 12 |  |  | — |  |  | 12 |
Other | — |  |  | 13 |  |  | — |  |  | — |  |  | 13 |
Total | $ | — |  |  | $ | 72 |  |  | $ | 12 |  |  | $ | — |  |  | $ | 84 |
Southern Company Gas |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |
Energy-related derivatives(a) | $ | 18 |  |  | $ | 10 |  |  | $ | — |  |  | $ | — |  |  | $ | 28 |
Non-qualified deferred compensation trusts: |  |  |  |  |  |  |  |  |
Domestic equity | — |  |  | 8 |  |  | — |  |  | — |  |  | 8 |
Foreign equity | — |  |  | 1 |  |  | — |  |  | — |  |  | 1 |
Pooled funds - fixed income | — |  |  | 7 |  |  | — |  |  | — |  |  | 7 |
Cash equivalents | 4 |  |  | — |  |  | — |  |  | — |  |  | 4 |
Cash equivalents | 50 |  |  | — |  |  | — |  |  | — |  |  | 50 |
Total | $ | 72 |  |  | $ | 26 |  |  | $ | — |  |  | $ | — |  |  | $ | 98 |
Liabilities: |  |  |  |  |  |  |  |  |
Energy-related derivatives(a)(b) | $ | 32 |  |  | $ | 33 |  |  | $ | — |  |  | $ | — |  |  | $ | 65 |
Interest rate derivatives | — |  |  | 86 |  |  | — |  |  | — |  |  | 86 |
Total | $ | 32 |  |  | $ | 119 |  |  | $ | — |  |  | $ | — |  |  | $ | 151 |
(a)Excludes cash collateral of $41 million. (b)Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 under "Nuclear Decommissioning" for additional information. (c)Includes investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. See Note 6 under "Nuclear Decommissioning" for additional information.
Financial instruments not having carrying amount equal to fair value | At December 31, 2023 and 2022, other financial instruments for which the carrying amount did not equal fair value were as follows:
| Southern Company(*) | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas(*)
| (in billions)
At December 31, 2023: |  |  |  |  |  |
Long-term debt, including securities due within one year: |  |  |  |  |  |
Carrying amount | $ | 59.4 |  | $ | 11.2 |  | $ | 16.5 |  | $ | 1.6 |  | $ | 2.7 |  | $ | 7.8 |
Fair value | 55.0 |  | 10.1 |  | 15.1 |  | 1.4 |  | 2.6 |  | 6.8 |
At December 31, 2022: |  |  |  |  |  |
Long-term debt, including securities due within one year: |  |  |  |  |  |
Carrying amount | $ | 54.6 |  | $ | 10.6 |  | $ | 14.7 |  | $ | 1.5 |  | $ | 3.0 |  | $ | 7.4 |
Fair value | 48.6 |  | 9.2 |  | 13.0 |  | 1.3 |  | 2.8 |  | 6.5 |
(*)The carrying amount of Southern Company Gas' long-term debt includes fair value adjustments from the effective date of the 2016 merger with Southern Company. Southern Company Gas amortizes the fair value adjustments over the remaining lives of the respective bonds, the latest being through 2043.

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