2.2.0.25truefalse060206 - Disclosure - Retirements Benefits (Details 7)truefalseIn Millionsfalse1falsefalseUSDtruefalse{us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis} : Other Post retirement Benefit Plans Defined Benefit [Member] 1/1/2010 - 12/31/2010 USD ($) $TwelveMonthsEnded_31Dec2010_Other_Postretirement_Benefit_Plans_Defined_Benefit_Memberhttp://www.sec.gov/CIK0000092122duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseOther Post retirement Benefit Plans Defined Benefit [Member]us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisexplicitMemberPureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2falsefalseUSDtruefalse{us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis} : Other Post retirement Benefit Plans Defined Benefit [Member] 1/1/2009 - 12/31/2009 USD ($) $TwelveMonthsEnded_31Dec2009_Other_Postretirement_Benefit_Plans_Defined_Benefit_Memberhttp://www.sec.gov/CIK0000092122duration2009-01-01T00:00:002009-12-31T00:00:00falsefalseOther Post retirement Benefit Plans Defined Benefit [Member]us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$3falsefalseUSDtruefalse{us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis} : Other Post retirement Benefit Plans Defined Benefit [Member] 1/1/2008 - 12/31/2008 USD ($) $TwelveMonthsEnded_31Dec2008_Other_Postretirement_Benefit_Plans_Defined_Benefit_Memberhttp://www.sec.gov/CIK0000092122duration2008-01-01T00:00:002008-12-31T00:00:00falsefalseOther Post retirement Benefit Plans Defined Benefit [Member]us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$2true0so_ComponentsOfOtherPostretirementBenefitPlansNetPeriodicCostAbstractsofalsenadurationComponents of the other postretirement benefit plans, net periodic cost.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringComponents of the other postretirement benefit plans, net periodic cost.falsefalseComponents of the other postretirement benefit plans, net periodic cost3false0us-gaap_DefinedBenefitPlanServiceCostus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse2500000025falsetruefalsefalsefalse2truefalsefalse2600000026falsetruefalsefalsefalse3truefalsefalse2800000028falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 106 -Paragraph 518 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 87 -Paragraph 264 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph a, h falsefalseService cost4false0us-gaap_DefinedBenefitPlanInterestCostus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse100000000100falsefalsefalsefalsefalse2truefalsefalse113000000113falsefalsefalsefalsefalse3truefalsefalse111000000111falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 106 -Paragraph 518 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 87 -Paragraph 264 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph a, h falsefalseInterest cost5false0us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssetsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-63000000-63falsefalsefalsefalsefalse2truefalsefalse-61000000-61falsefalsefalsefalsefalse3truefalsefalse-59000000-59falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAn amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 106 -Paragraph 518 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 87 -Paragraph 264 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph h falsefalseExpected return on plan assets6false0us-gaap_DefinedBenefitPlanAmortizationOfGainsLossesus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse2000000020falsefalsefalsefalsefalse2truefalsefalse2500000025falsefalsefalsefalsefalse3truefalsefalse3100000031falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of gains or losses recognized in net periodic benefit costReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph h falsefalseNet amortization7false0us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse8200000082falsefalsefalsefalsefalse2truefalsefalse103000000103falsefalsefalsefalsefalse3truefalsefalse111000000111falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph h falsefalseNet postretirement cost8true0so_SummaryOfEstimationOfFutureBenefitPaymentsAndSubsidyReceiptsBasedOnAssumptionsUsedToMeasureAccumulatedBenefitObligationForPostretirementPlansAbstractsofalsenadurationSummary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringSummary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans abstract.falsefalseSummary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans9false0us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsInYearOneus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse108000000108falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of the benefits expected to be paid in Year 1.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseBenefit Payments for 201110false0us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsInYearTwous-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse114000000114falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of the benefits expected to be paid in Year 2.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseBenefit Payments for 201211false0us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsInYearThreeus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse121000000121falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of the benefits expected to be paid in Year 3.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseBenefit Payments for 201312false0us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsInYearFourus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse127000000127falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of the benefits expected to be paid in Year 4.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseBenefit Payments for 201413false0us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsInYearFiveus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse133000000133falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of the benefits expected to be paid in Year 5.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseBenefit Payments for 201514false0us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsInFiveFiscalYearsThereafterus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse695000000695falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of the aggregate benefits expected to be paid in the five fiscal years thereafter (the aggregate amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f truefalseBenefit Payments for 2016 to 202015false0us-gaap_PrescriptionDrugSubsidyReceiptsYearOneus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-8000000-8falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAmount of the prescription drug subsidy receipts expected to be received in Year 1 after the balance sheet date.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS106-2 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseSubsidy Receipts for 201116false0us-gaap_PrescriptionDrugSubsidyReceiptsYearTwous-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-9000000-9falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAmount of the prescription drug subsidy receipts expected to be received in Year 2 after the balance sheet date.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS106-2 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseSubsidy Receipts for 201217false0us-gaap_PrescriptionDrugSubsidyReceiptsYearThreeus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-10000000-10falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAmount of the prescription drug subsidy receipts expected to be received in Year 3 after the balance sheet date.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS106-2 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseSubsidy Receipts for 201318false0us-gaap_PrescriptionDrugSubsidyReceiptsYearFourus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-12000000-12falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAmount of the prescription drug subsidy receipts expected to be received in Year 4 after the balance sheet date.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS106-2 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseSubsidy Receipts for 201419false0us-gaap_PrescriptionDrugSubsidyReceiptsYearFiveus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-13000000-13falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAmount of the prescription drug subsidy receipts expected to be received in Year 5 after the balance sheet date.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS106-2 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f falsefalseSubsidy Receipts for 201520false0us-gaap_PrescriptionDrugSubsidyReceiptsFiveFiscalYearsThereafterus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse-69000000-69falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAggregate amount for the next five fiscal years following the first five fiscal years (that is the aggregate of fiscal years six through ten) following the balance sheet date of the prescription drug subsidy receipts expected to be received.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS106-2 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph f truefalseSubsidy Receipts for 2016 to 202021false0so_DefinedBenefitPlanExpectedFutureBenefitPaymentsAndSubsidyReceiptsTotalInYearOnesofalsedebitinstantDefined benefit plan expected future benefit 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available.falsefalseTotal for 201223false0so_DefinedBenefitPlanExpectedFutureBenefitPaymentsAndSubsidyReceiptsTotalInYearThreesofalsedebitinstantDefined benefit plan expected future benefit payments and subsidy receipts total in year three.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse111000000111falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryDefined benefit plan expected future benefit payments and subsidy receipts total in year three.No authoritative reference available.falsefalseTotal for 201324false0so_DefinedBenefitPlanExpectedFutureBenefitPaymentsAndSubsidyReceiptsTotalInYearFoursofalsedebitinstantDefined benefit plan expected future benefit payments and subsidy receipts total in year 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201526false0so_DefinedBenefitPlanExpectedFutureBenefitPaymentsAndSubsidyReceiptsTotalInFiveFiscalYearsThereaftersofalsedebitinstantDefined benefit plan expected future benefit payments and subsidy receipts total in five fiscal years thereafter.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse626000000626falsetruefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryDefined benefit plan expected future benefit payments and subsidy receipts total in five fiscal years thereafter.No authoritative reference available.truefalseTotal for 2016 to 2020325Retirements Benefits (Details 7) (Other Post retirement Benefit Plans Defined Benefit [Member], USD $)MillionsUnKnownUnKnownUnKnownfalsetrue