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REVENUE FROM CONTRACTS WITH CUSTOMERS - Contract Balances (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Disaggregation of Revenue [Line Items] |  |
Accounts Receivable | $ 2,820 | $ 3,123
Contract Assets | 271 | 156
Contract Liabilities | 116 | 45
Contract with customer, liability, revenue recognized | 36 | 36
Unregulated Distributed Generation |  |
Disaggregation of Revenue [Line Items] |  |
Contract Assets | 91 | 65
Contract Liabilities | 115 | 32
Alabama Power |  |
Disaggregation of Revenue [Line Items] |  |
Accounts Receivable | 821 | 696
Contract Assets | 2 | 2
Contract Liabilities | 0 | 4
Georgia Power |  |
Disaggregation of Revenue [Line Items] |  |
Accounts Receivable | 1,011 | 922
Contract Assets | 121 | 89
Contract Liabilities | 1 | 9
Mississippi Power |  |
Disaggregation of Revenue [Line Items] |  |
Accounts Receivable | 90 | 92
Contract Assets | 0 | 0
Contract Liabilities | 0 | 0
Southern Power |  |
Disaggregation of Revenue [Line Items] |  |
Accounts Receivable | 122 | 237
Contract Assets | 0 | 0
Contract Liabilities | 4 | 1
Southern Company Gas |  |
Disaggregation of Revenue [Line Items] |  |
Accounts Receivable | 684 | 1,107
Contract Assets | 56 | 0
Contract Liabilities | 0 | $ 0
Southern Company Gas | Energy Efficiency Enhancement And Upgrade |  |
Disaggregation of Revenue [Line Items] |  |
Contract Liabilities | $ 59 |

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