2.2.0.25truefalse060210 - Disclosure - Retirement Benefits (Details) (Textual)truefalsefalse1falsefalseUSDfalsefalse1/1/2010 - 12/31/2010 USD ($) USD ($) / shares $Jan-01-2010_Dec-31-2010http://www.sec.gov/CIK0000092122duration2010-01-01T00:00:002010-12-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDEPSDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2falsefalseUSDfalsefalse1/1/2009 - 12/31/2009 USD ($) USD ($) / shares $TwelveMonthsEnded_31Dec2009http://www.sec.gov/CIK0000092122duration2009-01-01T00:00:002009-12-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDEPSDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0USDUSD$3falsefalseUSDfalsefalse1/1/2008 - 12/31/2008 USD ($) USD ($) / shares $TwelveMonthsEnded_31Dec2008http://www.sec.gov/CIK0000092122duration2008-01-01T00:00:002008-12-31T00:00:00PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDEPSDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$4falsefalsefalsefalse1/1/2007 - 12/31/2007 TwelveMonthsEnded_31Dec2007http://www.sec.gov/CIK0000092122duration2007-01-01T00:00:002007-12-31T00:00:00PureStandardhttp://www.xbrl.org/2003/instancepurexbrli02true0so_RetirementBenefitsTextualAbstractsofalsenadurationRetirement Benefits Textual Abstract.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRetirement Benefits Textual Abstract.falsefalseRetirement Benefits [Textual] [Abstract]3false0us-gaap_DefinedBenefitPlanAccumulatedBenefitObligationus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse67000000006700000000falsetruefalsefalsefalse2truefalsefalse63000000006300000000falsetruefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph e falsefalseTotal accumulated benefit obligation for the pension plans4true0so_RetirementBenefitsTextualsAbstractsofalsenadurationRetirement Benefits.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRetirement Benefits.falsefalseRetirement Benefits (Textuals) [Abstract]5false0so_VoluntaryContributionToPensionPlansofalsedebitdurationVoluntary contribution to pension plan.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse620000000620000000falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryVoluntary contribution to pension plan.No authoritative reference available.falsefalseVoluntary contribution to pension plan6false0us-gaap_DefinedBenefitPlanEstimatedFutureEmployerContributionsInNextFiscalYearus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse3100000031000000falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph g falsefalseExpected other postretirement trust contributions7false0us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRateus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsetruefalse00falsefalsefalsefalsefalse2falsetruefalse00falsefalsefalsefalsefalse3falsetruefalse00falsefalsefalsefalsefalse4truetruefalse0.06300.0630falsefalsefalsefalsefalseOtherus-types:percentItemTypepureThe interest rate used to adjust for the time value of money.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph j falsefalseDiscount rate on net periodic benefit costs8false0us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncreaseus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.03840.0384falsefalsefalsefalsefalse2truetruefalse0.04180.0418falsefalsefalsefalsefalse3truetruefalse0.03750.0375falsefalsefalsefalsefalse4truetruefalse0.03750.0375falsefalsefalsefalsefalseOtherus-types:percentItemTypepureExpected rate of compensation increases (for pay-related plans).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph j falsefalsePercentage of annual increase in salary used for calculating net periodic benefit cost9false0us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYearus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.08250.0825falsefalsefalsefalsefalse2falsetruefalse00falsefalsefalsefalsefalse3falsetruefalse00falsefalsefalsefalsefalse4falsetruefalse00falsefalsefalsefalsefalseOtherus-types:percentItemTypepureThe assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph l falsefalseWeighted average medical care cost trend rate10false0us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRateus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.0500.050falsefalsefalsefalsefalse2falsetruefalse00falsefalsefalsefalsefalse3falsetruefalse00falsefalsefalsefalsefalse4falsetruefalse00falsefalsefalsefalsefalseOtherus-types:percentItemTypepureThe ultimate trend rate for health care costs.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph l falsefalseWeighted average medical care cost trend rate decreasing gradually through 2019 and remaining11false0so_AnnualIncreaseOrDecreaseInAssumedMedicalCareCostTrendRatesofalsenadurationAnnual Increase Or Decrease In The Assumed Medical Care Cost Trend Rate.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.010.01falsefalsefalsefalsefalse2falsetruefalse00falsefalsefalsefalsefalse3falsetruefalse00falsefalsefalsefalsefalse4falsetruefalse00falsefalsefalsefalsefalseOtherus-types:percentItemTypepureAnnual Increase Or Decrease In The Assumed Medical Care Cost Trend Rate.No authoritative reference available.falsefalseAnnual increase or decrease in the assumed medical care cost trend rate12false0so_PeriodOverWhichCompanyHasElectedToAmortizeChangesInMarketValueOfAllPlanAssetssofalsenadurationPeriod Over Which Company Has Elected To Amortize Changes In The Market Value Of All Plan Assets.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00over five yearsfalsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringPeriod Over Which Company Has Elected To Amortize Changes In The Market Value Of All Plan Assets.No authoritative reference available.falsefalsePeriod over which company has elected to amortize changes in the market value of all plan assets13false0so_PercentageOfPrescriptionDrugSubsidyForMedicareEligibleRetireessofalsenadurationPercentage Of Prescription Drug Subsidy For Medicare Eligible Retirees.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.280.28falsefalsefalsefalsefalse2falsetruefalse00falsefalsefalsefalsefalse3falsetruefalse00falsefalsefalsefalsefalse4falsetruefalse00falsefalsefalsefalsefalseOtherus-types:percentItemTypepurePercentage Of Prescription Drug Subsidy For Medicare Eligible Retirees.No authoritative reference available.falsefalsePercentage of prescription drug subsidy for Medicare eligible retirees14false0so_ReductionInExpensesDueToSubsidyEffectOfMedicalPrescriptionDrugsofalsecreditdurationReduction in expenses due to subsidy effect of medical prescription Drug.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse2800000028000000falsefalsefalsefalsefalse2truefalsefalse3300000033000000falsefalsefalsefalsefalse3truefalsefalse3500000035000000falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryReduction in expenses due to subsidy effect of medical prescription Drug.No authoritative reference available.falsefalseReduction in expenses due to subsidy effect of medical prescription Drug15false0so_PerformanceOfExtensiveStudyBasedOnProjectionsOfBothAssetsAndLiabilitiesForDeterminingOptimalAssetAllocationForPensionFundsofalsenadurationPerformance Of Extensive Study Based On Projections Of Both Assets And Liabilities For Determining The Optimal Asset...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Over a 10-year forward horizonfalsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringPerformance Of Extensive Study Based On Projections Of Both Assets And Liabilities For Determining The Optimal Asset Allocation For The Pension Fund.No authoritative reference available.falsefalsePerformance of extensive study based on projections of both assets and liabilities for determining the optimal asset allocation for the pension fund16false0so_PeriodAtWhichExternalInvestmentManagersTypicallySendValuationsToBothCustodianAndToCompanyAfterQuarterEndsofalsenadurationPeriod At Which The External Investment Managers Typically Send Valuations To Both The Custodian And To The Company After The...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00within 90 daysfalsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringPeriod At Which The External Investment Managers Typically Send Valuations To Both The Custodian And To The Company After The Quarter End.No authoritative reference available.falsefalsePeriod at which the external investment managers typically send valuations to both the custodian and to the Company after the quarter end17false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://southerncompany.com/role/retirementbenefitsdetailstextual1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalse5falsefalseUSDtruefalse{us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis} : Qualified Pension Plans [Member] 12/31/2010 USD ($) $BalanceAsOf_31Dec2010_Qualified_Pension_Plans_Memberhttp://www.sec.gov/CIK0000092122instant2010-12-31T00:00:000001-01-01T00:00:00falsefalseQualified Pension Plans [Member]us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisxbrldihttp://xbrl.org/2006/xbrldiso_QualifiedPensionPlansMemberus-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseQualified Pension Plans [Member]18true0so_RetirementBenefitsTextualAbstractsofalsenadurationRetirement Benefits Textual Abstract.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRetirement Benefits Textual Abstract.falsefalseRetirement Benefits [Textual] [Abstract]19false0us-gaap_DefinedBenefitPlanBenefitObligationus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse67000000006700000000falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetary1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. The projected benefit obligation is measured using assumptions as to future compensation levels if the pension benefit formula is based on those future compensation levels (pay-related, final-pay, final-average-pay, or career-average-pay plans). For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date. Prior to an employee's full eligibility date, the accumulated postretirement benefit obligation as of a particular date for an employee is the portion of the expected postretirement benefit obligation attributed to that employee's service rendered to that date; on and after the full eligibility date, the accumulated and expected postretirement benefit obligations for an employee are the same.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph a Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 6 -Subparagraph a Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph E1 falsefalseProjected benefit obligations21false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://southerncompany.com/role/retirementbenefitsdetailstextual1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalse6falsefalseUSDtruefalse{us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis} : Non Qualified Pension Plans [Member] 12/31/2010 USD ($) $BalanceAsOf_31Dec2010_Non_Qualified_Pension_Plans_Memberhttp://www.sec.gov/CIK0000092122instant2010-12-31T00:00:000001-01-01T00:00:00falsefalseNon Qualified Pension Plans [Member]us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisxbrldihttp://xbrl.org/2006/xbrldiso_NonQualifiedPensionPlansMemberus-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseNon Qualified Pension Plans [Member]22true0so_RetirementBenefitsTextualAbstractsofalsenadurationRetirement Benefits Textual Abstract.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRetirement Benefits Textual Abstract.falsefalseRetirement Benefits [Textual] [Abstract]23false0us-gaap_DefinedBenefitPlanBenefitObligationus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse500000000500000000falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetary1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. The projected benefit obligation is measured using assumptions as to future compensation levels if the pension benefit formula is based on those future compensation levels (pay-related, final-pay, final-average-pay, or career-average-pay plans). For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date. Prior to an employee's full eligibility date, the accumulated postretirement benefit obligation as of a particular date for an employee is the portion of the expected postretirement benefit obligation attributed to that employee's service rendered to that date; on and after the full eligibility date, the accumulated and expected postretirement benefit obligations for an employee are the same.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph a Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 6 -Subparagraph a Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph E1 falsefalseProjected benefit obligations25false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://southerncompany.com/role/retirementbenefitsdetailstextual1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalse7falsefalseUSDtruefalse{us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis} : Employee Saving Plan [Member] 1/1/2010 - 12/31/2010 USD ($) $TwelveMonthsEnded_31Dec2010_Employee_Saving_Plan_Memberhttp://www.sec.gov/CIK0000092122duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseEmployee Saving Plan [Member]us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisxbrldihttp://xbrl.org/2006/xbrldiso_EmployeeSavingPlanMemberus-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisexplicitMemberPureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$8falsefalseUSDtruefalse{us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis} : Employee Saving Plan [Member] 1/1/2009 - 12/31/2009 USD ($) $TwelveMonthsEnded_31Dec2009_Employee_Saving_Plan_Memberhttp://www.sec.gov/CIK0000092122duration2009-01-01T00:00:002009-12-31T00:00:00falsefalseEmployee Saving Plan [Member]us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisxbrldihttp://xbrl.org/2006/xbrldiso_EmployeeSavingPlanMemberus-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$9falsefalseUSDtruefalse{us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis} : Employee Saving Plan [Member] 1/1/2008 - 12/31/2008 USD ($) $TwelveMonthsEnded_31Dec2008_Employee_Saving_Plan_Memberhttp://www.sec.gov/CIK0000092122duration2008-01-01T00:00:002008-12-31T00:00:00falsefalseEmployee Saving Plan [Member]us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisxbrldihttp://xbrl.org/2006/xbrldiso_EmployeeSavingPlanMemberus-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseEmployee Saving Plan [Member]26true0so_RetirementBenefitsTextualAbstractsofalsenadurationRetirement Benefits Textual Abstract.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRetirement Benefits Textual Abstract.falsefalseRetirement Benefits [Textual] [Abstract]27false0so_MatchingLimitOfContributionByEmployersofalsenadurationMatching limit of contribution by employer.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.850.85falsefalsefalsefalsefalse2falsetruefalse00falsefalsefalsefalsefalse3falsetruefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherus-types:percentItemTypepureMatching limit of contribution by employer.No authoritative reference available.falsefalseMatching limit of contribution by employer28false0so_MaximumLimitOfContributionOfEmployeesBaseSalarysofalsenadurationMaximum Limit Of Contribution Of Employees Base Salary.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.060.06falsefalsefalsefalsefalse2falsetruefalse00falsefalsefalsefalsefalse3falsetruefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherus-types:percentItemTypepureMaximum Limit Of Contribution Of Employees Base Salary.No authoritative reference available.falsefalseMaximum limit of contribution of employees base salary29false0us-gaap_DefinedBenefitPlanContributionsByEmployerus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse7600000076000000falsetruefalsefalsefalse2truefalsefalse7800000078000000falsetruefalsefalsefalse3truefalsefalse7600000076000000falsetruefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of contributions made by the employer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph b falsefalseTotal matching contributions426Retirement Benefits (Details) (Textual) (USD $)NoRoundingUnKnownUnKnownUnKnowntruetrue