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FINANCING - Bank Credit Arrangements Narrative (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020
Line of Credit Facility [Line Items] |  |
Ratio of indebtedness to capitalization, debt covenant, required | 70.00% |
Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support | $ 1,500 |
Other Subsidiaries |  |
Line of Credit Facility [Line Items] |  |
Ratio of indebtedness to capitalization, debt covenant, required | 65.00% |
Alabama Power |  |
Line of Credit Facility [Line Items] |  |
Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support | $ 789 |
Georgia Power |  |
Line of Credit Facility [Line Items] |  |
Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support | 672 |
Remarketed pollution control bonds | 157 |
Mississippi Power |  |
Line of Credit Facility [Line Items] |  |
Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support | 34 |
Southern Power | Power Purchase Agreement |  |
Line of Credit Facility [Line Items] |  |
Debt instrument, collateral amount | $ 105 | $ 105

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