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Fair Value Measurements - Schedule of Increase (Decrease) In Fair Value Of Funds (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |  |
Increase (decrease) in fair value of funds | $ 132 | $ (230) | $ 228 | $ (380)
ALABAMA POWER CO |  |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |  |
Increase (decrease) in fair value of funds | 58 | (125) | 103 | (192)
GEORGIA POWER CO |  |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |  |
Increase (decrease) in fair value of funds | $ 74 | $ (105) | $ 125 | $ (188)

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