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CONTINGENCIES, COMMITMENTS, AND GUARANTEES - Environmental Remediation (Details) | 12 Months Ended
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Dec. 31, 2023 USD ($) site state | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Georgia Power |  |  |
Environmental Exit Cost [Line Items] |  |  |
Costs recovered annually | $ 5,000,000 | $ 12,000,000 | $ 12,000,000
Environmental remediation liability, current | 14,000,000 | 15,000,000 |
Accrued environmental remediation | 0 | 0 |
Under recovered environmental remediation costs, other regulatory assets, current | 5,000,000 | 5,000,000 |
Under recovered environmental remediation costs, other regulatory assets, deferred | 15,000,000 | 20,000,000 |
Southern Company Gas |  |  |
Environmental Exit Cost [Line Items] |  |  |
Environmental remediation liability, current | 30,000,000 | 49,000,000 |
Accrued environmental remediation | 192,000,000 | 207,000,000 |
Under recovered environmental remediation costs, other regulatory assets, current | 40,000,000 | 54,000,000 |
Under recovered environmental remediation costs, other regulatory assets, deferred | $ 195,000,000 | 215,000,000 |
Southern Company Gas | Manufactured Gas Plants |  |  |
Environmental Exit Cost [Line Items] |  |  |
Number of sites | site | 40 |  |
Number of states in which subject to environmental remediation liabilities | state | 4 |  |
Alabama Power |  |  |
Environmental Exit Cost [Line Items] |  |  |
Environmental remediation liability, current | $ 0 | 0 |
Southern Company |  |  |
Environmental Exit Cost [Line Items] |  |  |
Environmental remediation liability, current | 44,000,000 | 65,000,000 |
Accrued environmental remediation | 192,000,000 | 207,000,000 |
Under recovered environmental remediation costs, other regulatory assets, current | 45,000,000 | 59,000,000 |
Under recovered environmental remediation costs, other regulatory assets, deferred | $ 210,000,000 | $ 235,000,000 |
Environmental Loss Contingency, Current, Statement of Financial Position [Extensible Enumeration] | Other Liabilities, Current |  |

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