2.2.0.25falsefalse06011 - Disclosure - Summary of Significant Accounting Policies (Details 1)truefalseIn Millionsfalse1falsefalseUSDfalsefalse12/31/2010 USD ($) $BalanceAsOf_31Dec2010http://www.sec.gov/CIK0000092122instant2010-12-31T00:00:000001-01-01T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$2falsefalseUSDfalsefalse12/31/2009 USD ($) $BalanceAsOf_31Dec2009http://www.sec.gov/CIK0000092122instant2009-12-31T00:00:000001-01-01T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$3true0us-gaap_PublicUtilitiesPropertyPlantAndEquipmentPlantInServiceAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseProperty, Plant, and Equipment4false0us-gaap_PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessingus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse3012100000030121falsetruefalsefalsefalse2truefalsefalse2820400000028204falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryPeriod end amount of property, plant and equipment (PPE) related to generation or processing owned by public utility.No authoritative reference available.falsefalseGeneration5false0us-gaap_PublicUtilitiesPropertyPlantAndEquipmentTransmissionus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse78350000007835falsefalsefalsefalsefalse2truefalsefalse73800000007380falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryPeriod end amount of property, plant and equipment (PPE) related to utility transmission owned by public utility.No authoritative reference available.falsefalseTransmission6false0us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistributionus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse1487000000014870falsefalsefalsefalsefalse2truefalsefalse1433500000014335falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryPeriod end amount of property, plant and equipment (PPE) related to utility distribution.No authoritative reference available.falsefalseDistribution7false0so_PublicUtilitiesPropertyPlantAndEquipmentGeneralsofalsedebitinstantPublic Utilities Property Plant And Equipment General.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse31160000003116falsefalsefalsefalsefalse2truefalsefalse29170000002917falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryPublic Utilities Property Plant And Equipment General.No authoritative reference available.falsefalseGeneral8false0us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustmentsus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse4300000043falsefalsefalsefalsefalse2truefalsefalse4300000043falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of acquisition adjustments included in property, plant and equipment (PPE) for utilities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 90 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial 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