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Derivatives - Schedule of Cumulative Basis Adjustments for Fair Value Hedges (Details) - Fair Value Hedging - Long-term debt - USD ($) $ in Millions | Jun. 30, 2023 | Dec. 31, 2022
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Derivative [Line Items] |  |
Carrying Amount of the Hedged Item | $ (2,970) | $ (2,927)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item | 265 | 282
SOUTHERN Co GAS |  |
Derivative [Line Items] |  |
Carrying Amount of the Hedged Item | (417) | (415)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item | $ 80 | $ 81

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