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These taxes could include production, real estate, personal property, and pump tax.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Taxes other than income taxes49false 5us-gaap_CostsAndExpensesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse10350000001035000000USD$falsefalsefalse2truefalsefalse987000000987000000USD$falsefalsefalse3truefalsefalse20360000002036000000USD$falsefalsefalse4truefalsefalse19120000001912000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryTotal costs of sales and operating expenses for the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 true2Total operating expenses50false 4us-gaap_OperatingIncomeLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse357000000357000000USD$falsefalsefalse2truefalsefalse390000000390000000USD$falsefalsefalse3truefalsefalse664000000664000000USD$falsefalsefalse4truefalsefalse681000000681000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net result for the period of deducting operating expenses from operating revenues.No definition available.true2Operating Income51true 4us-gaap_NonoperatingIncomeExpenseAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Other Income and (Expense):52false 5us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquityus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse80000008000000USD$falsefalsefalse2truefalsefalse40000004000000USD$falsefalsefalse3truefalsefalse1600000016000000USD$falsefalsefalse4truefalsefalse90000009000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430 false2Allowance for equity funds used during construction53false 5us-gaap_InterestAndDebtExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-65000000-65000000USD$falsefalsefalse2truefalsefalse-73000000-73000000USD$falsefalsefalse3truefalsefalse-131000000-131000000USD$falsefalsefalse4truefalsefalse-146000000-146000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInterest and debt related expenses associated with nonoperating financing activities of the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391 false2Interest expense, net of amounts capitalized54false 5us-gaap_OtherNonoperatingIncomeExpenseus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse20000002000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalse3truefalsefalse10000001000000USD$falsefalsefalse4truefalsefalse-3000000-3000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. 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Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 true2Total operating revenues68true 4us-gaap_CostsAndExpensesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Expenses:69false 5us-gaap_UtilitiesOperatingExpenseFuelUsedus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse557000000557000000USD$falsefalsefalse2truefalsefalse572000000572000000USD$falsefalsefalse3truefalsefalse10760000001076000000USD$falsefalsefalse4truefalsefalse10120000001012000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating expense for fuel used by regulated operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Fuel70false 5so_CostOfPurchasedPowerNonAffiliatesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse6100000061000000USD$falsefalsefalse2truefalsefalse9400000094000000USD$falsefalsefalse3truefalsefalse111000000111000000USD$falsefalsefalse4truefalsefalse187000000187000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of electricity purchased from non-affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period.No definition available.false2Purchased power, non-affiliates71false 5so_CostOfPurchasedPowerAffiliatesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse176000000176000000USD$falsefalsefalse2truefalsefalse129000000129000000USD$falsefalsefalse3truefalsefalse351000000351000000USD$falsefalsefalse4truefalsefalse288000000288000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of electricity purchased from affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period.No definition available.false2Purchased power, affiliates72false 5us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperationsus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse397000000397000000USD$falsefalsefalse2truefalsefalse411000000411000000USD$falsefalsefalse3truefalsefalse828000000828000000USD$falsefalsefalse4truefalsefalse845000000845000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating expense for routine plant maintenance, repairs and operations of regulated operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Other operations and maintenance73false 5so_DepreciationAndAmortizationExcludingNuclearFuelso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse204000000204000000USD$falsefalsefalse2truefalsefalse185000000185000000USD$falsefalsefalse3truefalsefalse404000000404000000USD$falsefalsefalse4truefalsefalse373000000373000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe current period expense charged against earnings on long-lived, physical assets used in the normal conduct of business and not intended for resale to allocate or recognize the cost of assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset. 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-URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591552-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686 true2Consolidated Net Income85false 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Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 true2Total operating revenues94true 4us-gaap_CostsAndExpensesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Expenses:95false 5us-gaap_UtilitiesOperatingExpenseFuelUsedus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse140347000140347000USD$falsefalsefalse2truefalsefalse141220000141220000USD$falsefalsefalse3truefalsefalse261193000261193000USD$falsefalsefalse4truefalsefalse262308000262308000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating expense for fuel used by regulated operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Fuel96false 5so_CostOfPurchasedPowerNonAffiliatesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse1305400013054000USD$falsefalsefalse2truefalsefalse1208500012085000USD$falsefalsefalse3truefalsefalse2418900024189000USD$falsefalsefalse4truefalsefalse2331000023310000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of electricity purchased from non-affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period.No definition available.false2Purchased power, non-affiliates97false 5so_CostOfPurchasedPowerAffiliatesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse1093400010934000USD$falsefalsefalse2truefalsefalse52100005210000USD$falsefalsefalse3truefalsefalse1424600014246000USD$falsefalsefalse4truefalsefalse77230007723000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of electricity purchased from affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period.No definition available.false2Purchased power, affiliates98false 5us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperationsus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse7684600076846000USD$falsefalsefalse2truefalsefalse7977900079779000USD$falsefalsefalse3truefalsefalse155508000155508000USD$falsefalsefalse4truefalsefalse155009000155009000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating expense for routine plant maintenance, repairs and operations of regulated operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Other operations and maintenance99false 5so_DepreciationAndAmortizationExcludingNuclearFuelso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse3708100037081000USD$falsefalsefalse2truefalsefalse3517300035173000USD$falsefalsefalse3truefalsefalse7413400074134000USD$falsefalsefalse4truefalsefalse6848000068480000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe current period expense charged against earnings on long-lived, physical assets used in the normal conduct of business and not intended for resale to allocate or recognize the cost of assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset. 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Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Other income (expense), net107false 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4us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterestus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse5498800054988000USD$falsefalsefalse2truefalsefalse5861500058615000USD$falsefalsefalse3truefalsefalse9241700092417000USD$falsefalsefalse4truefalsefalse9257300092573000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 10 -Article 5 false2Earnings Before Income Taxes109false 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http://asc.fasb.org/extlink&oid=31814832&loc=SL4591552-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686 true2Consolidated Net Income111false 4us-gaap_PreferredStockDividendsIncomeStatementImpactus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse16510001651000USD$falsefalsefalse2truefalsefalse15500001550000USD$falsefalsefalse3truefalsefalse32020003202000USD$falsefalsefalse4truefalsefalse31010003101000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of preferred stock dividends that is an adjustment to net income apportioned to common stockholders.No definition available.false2Dividends on Preferred and Preference Stock112false 4us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse3258200032582000USD$falsefalsefalse2truefalsefalse3496300034963000USD$falsefalsefalse3truefalsefalse5437400054374000USD$falsefalsefalse4truefalsefalse5562900055629000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryNet income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e1377-109256 true2Consolidated Net Income After Dividends on Preferred and Preference Stock of Subsidiaries113false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse17false USDtruefalse$D2013Q2_dei_LegalEntityAxis_so_MississippiPowerMemberhttp://www.sec.gov/CIK0000092122duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseMississippi Power [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldiso_MississippiPowerMemberdei_LegalEntityAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Mississippi Power [Member]114true 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false2Other revenues119false 5us-gaap_Revenuesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse306435000306435000USD$falsefalsefalse2truefalsefalse266084000266084000USD$falsefalsefalse3truefalsefalse552369000552369000USD$falsefalsefalse4truefalsefalse494798000494798000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 true2Total operating revenues120true 4us-gaap_CostsAndExpensesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Expenses:121false 5us-gaap_UtilitiesOperatingExpenseFuelUsedus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse142193000142193000USD$falsefalsefalse2truefalsefalse105469000105469000USD$falsefalsefalse3truefalsefalse246757000246757000USD$falsefalsefalse4truefalsefalse194088000194088000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating expense for fuel used by regulated operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Fuel122false 5so_CostOfPurchasedPowerNonAffiliatesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse17780001778000USD$falsefalsefalse2truefalsefalse11340001134000USD$falsefalsefalse3truefalsefalse31450003145000USD$falsefalsefalse4truefalsefalse30770003077000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of electricity purchased from non-affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period.No definition available.false2Purchased power, non-affiliates123false 5so_CostOfPurchasedPowerAffiliatesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse39220003922000USD$falsefalsefalse2truefalsefalse1084300010843000USD$falsefalsefalse3truefalsefalse1361100013611000USD$falsefalsefalse4truefalsefalse1970300019703000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of electricity purchased from affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period.No definition available.false2Purchased power, affiliates124false 5us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperationsus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse5445600054456000USD$falsefalsefalse2truefalsefalse6050100060501000USD$falsefalsefalse3truefalsefalse109268000109268000USD$falsefalsefalse4truefalsefalse115396000115396000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating expense for routine plant maintenance, repairs and operations of regulated operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Other operations and maintenance125false 5so_DepreciationAndAmortizationExcludingNuclearFuelso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2220900022209000USD$falsefalsefalse2truefalsefalse2251700022517000USD$falsefalsefalse3truefalsefalse4544200045442000USD$falsefalsefalse4truefalsefalse4499800044998000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe current period expense charged against earnings on long-lived, physical assets used in the normal conduct of business and not intended for resale to allocate or recognize the cost of assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset. 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-URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591552-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686 true2Consolidated Net Income138false 4us-gaap_PreferredStockDividendsIncomeStatementImpactus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse433000433000USD$falsefalsefalse2truefalsefalse433000433000USD$falsefalsefalse3truefalsefalse866000866000USD$falsefalsefalse4truefalsefalse866000866000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of preferred stock dividends that is an adjustment to net income apportioned to common stockholders.No definition available.false2Dividends on Preferred and Preference Stock139false 4us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-219110000-219110000USD$falsefalsefalse2truefalsefalse3502700035027000USD$falsefalsefalse3truefalsefalse-465431000-465431000USD$falsefalsefalse4truefalsefalse6028200060282000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryNet income after adjustments for dividends on preferred stock (declared in the period) and/or 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4us-gaap_RevenuesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Revenues:142false 5so_WholesaleRevenuesNonAffiliatesso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse216647000216647000USD$falsefalsefalse2truefalsefalse177865000177865000USD$falsefalsefalse3truefalsefalse440076000440076000USD$falsefalsefalse4truefalsefalse318422000318422000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryNon affiliated revenues from sales of energy supplied by one producer or marketer to another for eventual resale to consumers.No definition available.false2Wholesale revenues, non-affiliates143false 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adjustments, returns, allowances, and discounts.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1(a),(d)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 false2Other revenues145false 5us-gaap_Revenuesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse307255000307255000USD$falsefalsefalse2truefalsefalse285805000285805000USD$falsefalsefalse3truefalsefalse610202000610202000USD$falsefalsefalse4truefalsefalse539486000539486000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 true2Total operating revenues146true 4us-gaap_CostsAndExpensesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Expenses:147false 5us-gaap_UtilitiesOperatingExpenseFuelUsedus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse110630000110630000USD$falsefalsefalse2truefalsefalse9155100091551000USD$falsefalsefalse3truefalsefalse230002000230002000USD$falsefalsefalse4truefalsefalse180629000180629000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating expense for fuel used by regulated operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Fuel148false 5so_CostOfPurchasedPowerNonAffiliatesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2230700022307000USD$falsefalsefalse2truefalsefalse2251400022514000USD$falsefalsefalse3truefalsefalse3688000036880000USD$falsefalsefalse4truefalsefalse4316400043164000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of electricity purchased from non-affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period.No definition available.false2Purchased power, non-affiliates149false 5so_CostOfPurchasedPowerAffiliatesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse62820006282000USD$falsefalsefalse2truefalsefalse29140002914000USD$falsefalsefalse3truefalsefalse1414700014147000USD$falsefalsefalse4truefalsefalse52540005254000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of electricity purchased from affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period.No definition available.false2Purchased power, affiliates150false 5us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperationsus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse6266100062661000USD$falsefalsefalse2truefalsefalse4020500040205000USD$falsefalsefalse3truefalsefalse113611000113611000USD$falsefalsefalse4truefalsefalse8859400088594000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating expense for routine plant maintenance, repairs and operations of regulated operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 false2Other operations and maintenance151false 5so_DepreciationAndAmortizationExcludingNuclearFuelso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse4489800044898000USD$falsefalsefalse2truefalsefalse3401600034016000USD$falsefalsefalse3truefalsefalse8505800085058000USD$falsefalsefalse4truefalsefalse6592900065929000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe current period expense charged against earnings on long-lived, physical assets used in the normal conduct of business and not intended for resale to allocate or recognize the cost of assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset. 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