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available.falsefalseDepreciation of cost of utility plant in service, composite straight-line rate19false0so_AccumulatedDepreciationForUtilityPlantInServiceTotalsofalsedebitinstantAccumulated depreciation for utility plant in service, total.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse1970000000019700000000falsefalsefalsefalsefalse2truefalsefalse1870000000018700000000falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAccumulated depreciation for utility plant in service, total.No authoritative reference available.falsefalseAccumulated depreciation for utility plant in service, total20false0so_DepreciationOfOriginalCostOfOtherPlantInServiceMinimumUsefulLiveInYearssofalsenadurationDepreciation of the original cost of other plant in service minimum useful live 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available.falsefalseProceeds from sale of securities held in external trust funds25false0so_AllowanceForFundsUsedDuringConstructionAndInterestCapitalizedNetOfIncomeTaxessofalsenadurationAllowance for funds used during construction and interest capitalized, net of income taxes as a percentage of net income.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.1250.125falsefalsefalsefalsefalse2truetruefalse0.1530.153falsefalsefalsefalsefalse3truetruefalse0.1120.112falsefalsefalsefalsefalseOtherus-types:percentItemTypepureAllowance for funds used during construction and interest capitalized, net of income taxes as a percentage of net income.No authoritative reference available.falsefalseAFUDC and interest capitalized, net of income taxes26false0us-gaap_InterestPaidNetus-gaaptruecreditdurationNo definition 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