<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.0.8</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>624</ContextCount>
  <ElementCount>375</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>126</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>14</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Condensed Consolidated Statements Of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CondensedConsolidatedStatementsOfIncome</Role>
      <ShortName>Condensed Consolidated Statements Of Income</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002000 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002501 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Condensed Consolidated Statements Of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CondensedConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Condensed Consolidated Statements Of Cash Flows</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Summary Of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary Of Significant Accounting Policies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Utility Rate Cases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/UtilityRateCases</Role>
      <ShortName>Utility Rate Cases</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Receivables</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/Receivables</Role>
      <ShortName>Receivables</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Benefit Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlans</Role>
      <ShortName>Benefit Plans</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Common Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CommonEquity</Role>
      <ShortName>Common Equity</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Redeemable Preferred Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/RedeemablePreferredStock</Role>
      <ShortName>Redeemable Preferred Stock</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/Investments</Role>
      <ShortName>Investments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Derivative Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DerivativeInstruments</Role>
      <ShortName>Derivative Instruments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Commitments And Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CommitmentsAndContingencies</Role>
      <ShortName>Commitments And Contingencies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Segments Of Business</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/SegmentsOfBusiness</Role>
      <ShortName>Segments Of Business</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Discontinued Operations And Assets And Liabilities Held For Sale</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DiscontinuedOperationsAndAssetsAndLiabilitiesHeldForSale</Role>
      <ShortName>Discontinued Operations And Assets And Liabilities Held For Sale</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Asset Retirement Obligations (AROs)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/AssetRetirementObligationsAros</Role>
      <ShortName>Asset Retirement Obligations (AROs)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - Related Parties</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/RelatedParties</Role>
      <ShortName>Related Parties</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2117100 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Summary Of Significant Accounting Policies (Policy)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/SummaryOfSignificantAccountingPoliciesPolicy</Role>
      <ShortName>Summary Of Significant Accounting Policies (Policy)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2301302 - Disclosure - Summary Of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/SummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary Of Significant Accounting Policies (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Receivables (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/ReceivablesTables</Role>
      <ShortName>Receivables (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Benefit Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansTables</Role>
      <ShortName>Benefit Plans (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - Common Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CommonEquityTables</Role>
      <ShortName>Common Equity (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/InvestmentsTables</Role>
      <ShortName>Investments (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Derivative Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DerivativeInstrumentsTables</Role>
      <ShortName>Derivative Instruments (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2312301 - Disclosure - Commitments And Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments And Contingencies (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - Segments Of Business (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/SegmentsOfBusinessTables</Role>
      <ShortName>Segments Of Business (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - Discontinued Operations And Assets And Liabilities Held For Sale (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DiscontinuedOperationsAndAssetsAndLiabilitiesHeldForSaleTables</Role>
      <ShortName>Discontinued Operations And Assets And Liabilities Held For Sale (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2315301 - Disclosure - Asset Retirement Obligations (AROs) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/AssetRetirementObligationsArosTables</Role>
      <ShortName>Asset Retirement Obligations (AROs) (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2316301 - Disclosure - Related Parties (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/RelatedPartiesTables</Role>
      <ShortName>Related Parties (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2317301 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2401403 - Disclosure - Summary Of Significant Accounting Policies (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/SummaryOfSignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2401404 - Disclosure - Summary Of Significant Accounting Policies (Regulatory Assets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/SummaryOfSignificantAccountingPoliciesRegulatoryAssetsDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Regulatory Assets) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2401405 - Disclosure - Summary Of Significant Accounting Policies (Regulatory Liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/SummaryOfSignificantAccountingPoliciesRegulatoryLiabilitiesDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Regulatory Liabilities) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2402401 - Disclosure - Utility Rate Cases (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/UtilityRateCasesNarrativeDetails</Role>
      <ShortName>Utility Rate Cases (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Receivables (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/ReceivablesNarrativeDetails</Role>
      <ShortName>Receivables (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - Receivables (Maximum And Average Outstanding Cash Proceeds) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/ReceivablesMaximumAndAverageOutstandingCashProceedsDetails</Role>
      <ShortName>Receivables (Maximum And Average Outstanding Cash Proceeds) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2403404 - Disclosure - Receivables (Receivables Sold Under The Agreement) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/ReceivablesReceivablesSoldUnderAgreementDetails</Role>
      <ShortName>Receivables (Receivables Sold Under The Agreement) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2403405 - Disclosure - Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/ReceivablesAdditionalAttributesOfReceivablesSoldUnderAgreementDetails</Role>
      <ShortName>Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Income Taxes (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/IncomeTaxesNarrativeDetails</Role>
      <ShortName>Income Taxes (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Income Taxes (Schedule Of Effective Income Tax Rates) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/IncomeTaxesScheduleOfEffectiveIncomeTaxRatesDetails</Role>
      <ShortName>Income Taxes (Schedule Of Effective Income Tax Rates) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - Income Taxes (Production Tax Credits (Net Of State Tax Impacts)) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/IncomeTaxesProductionTaxCreditsNetOfStateTaxImpactsDetails</Role>
      <ShortName>Income Taxes (Production Tax Credits (Net Of State Tax Impacts)) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2404405 - Disclosure - Income Taxes (Summary Of Tax Credit Carryforwards) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/IncomeTaxesSummaryOfTaxCreditCarryforwardsDetails</Role>
      <ShortName>Income Taxes (Summary Of Tax Credit Carryforwards) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Benefit Plans (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansNarrativeDetails</Role>
      <ShortName>Benefit Plans (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2405403 - Disclosure - Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansDefinedBenefitPensionAndOtherPostretirementBenefitsPlansDetails</Role>
      <ShortName>Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2405404 - Disclosure - Benefit Plans (Schedule Of Qualified and Non-qualified Pension And Other Postretirement Benefits Costs (Credits)) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansScheduleOfQualifiedAndNonQualifiedPensionAndOtherPostretirementBenefitsCostsCreditsDetails</Role>
      <ShortName>Benefit Plans (Schedule Of Qualified and Non-qualified Pension And Other Postretirement Benefits Costs (Credits)) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2405405 - Disclosure - Benefit Plans (Estimated Future And Actual Employer Contributions) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansEstimatedFutureAndActualEmployerContributionsDetails</Role>
      <ShortName>Benefit Plans (Estimated Future And Actual Employer Contributions) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2405406 - Disclosure - Benefit Plans (Employees Participate In Defined Contribution Retirement Plans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansEmployeesParticipateInDefinedContributionRetirementPlansDetails</Role>
      <ShortName>Benefit Plans (Employees Participate In Defined Contribution Retirement Plans) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2405407 - Disclosure - Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansRecognizedCompensationExpenseAndIncomeTaxBenefitsDetails</Role>
      <ShortName>Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2405408 - Disclosure - Benefit Plans (Summary Of Performance Shares Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansSummaryOfPerformanceSharesActivityDetails</Role>
      <ShortName>Benefit Plans (Summary Of Performance Shares Activity) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2405409 - Disclosure - Benefit Plans (Summary Of Performance Unit Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansSummaryOfPerformanceUnitActivityDetails</Role>
      <ShortName>Benefit Plans (Summary Of Performance Unit Activity) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2405410 - Disclosure - Benefit Plans (Fair Values Of Nonvested Performance Shares And Units) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansFairValuesOfNonvestedPerformanceSharesAndUnitsDetails</Role>
      <ShortName>Benefit Plans (Fair Values Of Nonvested Performance Shares And Units) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2405411 - Disclosure - Benefit Plans (Summary Of Restricted Stock Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansSummaryOfRestrictedStockActivityDetails</Role>
      <ShortName>Benefit Plans (Summary Of Restricted Stock Activity) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2405412 - Disclosure - Benefit Plans (Summary Of Performance Contingent Cash Awards Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/BenefitPlansSummaryOfPerformanceContingentCashAwardsActivityDetails</Role>
      <ShortName>Benefit Plans (Summary Of Performance Contingent Cash Awards Activity) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - Common Equity (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CommonEquityNarrativeDetails</Role>
      <ShortName>Common Equity (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2406403 - Disclosure - Common Equity (Common Share Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CommonEquityCommonShareActivityDetails</Role>
      <ShortName>Common Equity (Common Share Activity) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2407401 - Disclosure - Redeemable Preferred Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/RedeemablePreferredStockDetails</Role>
      <ShortName>Redeemable Preferred Stock (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Debt (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DebtNarrativeDetails</Role>
      <ShortName>Debt (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - Debt (Credit Facilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DebtCreditFacilitiesDetails</Role>
      <ShortName>Debt (Credit Facilities) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2408404 - Disclosure - Debt (Other Short-Term Borrowings) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DebtOtherShortTermBorrowingsDetails</Role>
      <ShortName>Debt (Other Short-Term Borrowings) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Investments (Unconsolidated Equity Investments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/InvestmentsUnconsolidatedEquityInvestmentsDetails</Role>
      <ShortName>Investments (Unconsolidated Equity Investments) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - Investments (Summary Financial Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/InvestmentsSummaryFinancialInformationDetails</Role>
      <ShortName>Investments (Summary Financial Information) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Fair Value Measurements (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/FairValueMeasurementsNarrativeDetails</Role>
      <ShortName>Fair Value Measurements (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - Fair Value Measurements (Fair Value Of Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/FairValueMeasurementsFairValueOfFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Measurements (Fair Value Of Financial Instruments) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>2410404 - Disclosure - Fair Value Measurements (Fair Value Measurements) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/FairValueMeasurementsFairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Measurements (Fair Value Measurements) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>2410405 - Disclosure - Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/FairValueMeasurementsFairValueMeasurementsUsingSignificantUnobservableInputsDetails</Role>
      <ShortName>Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Derivative Instruments (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DerivativeInstrumentsNarrativeDetails</Role>
      <ShortName>Derivative Instruments (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DerivativeInstrumentsNotionalAmountsOfDerivativeInstrumentsDetails</Role>
      <ShortName>Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>2411404 - Disclosure - Derivative Instruments (Fair Value Of Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DerivativeInstrumentsFairValueOfFinancialInstrumentsDetails</Role>
      <ShortName>Derivative Instruments (Fair Value Of Financial Instruments) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>2411405 - Disclosure - Derivative Instruments (Gains And Losses From Derivative Instruments Not Designated As Hedging Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DerivativeInstrumentsGainsAndLossesFromDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsDetails</Role>
      <ShortName>Derivative Instruments (Gains And Losses From Derivative Instruments Not Designated As Hedging Instruments) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>2411406 - Disclosure - Derivative Instruments Derivative Instruments (Balance Sheet Offsetting) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DerivativeInstrumentsDerivativeInstrumentsBalanceSheetOffsettingDetails</Role>
      <ShortName>Derivative Instruments Derivative Instruments (Balance Sheet Offsetting) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>2412402 - Disclosure - Commitments And Contingencies (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CommitmentsAndContingenciesNarrativeDetails</Role>
      <ShortName>Commitments And Contingencies (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>2412403 - Disclosure - Commitments And Contingencies (Operating Expense Purchase Obligations) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/CommitmentsAndContingenciesOperatingExpensePurchaseObligationsDetails</Role>
      <ShortName>Commitments And Contingencies (Operating Expense Purchase Obligations) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - Segments Of Business (Schedule Of Segment Of Business) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/SegmentsOfBusinessScheduleOfSegmentOfBusinessDetails</Role>
      <ShortName>Segments Of Business (Schedule Of Segment Of Business) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - Discontinued Operations And Assets And Liabilities Held For Sale (Components Of Discontinued Operations In Condensed Consolidated Statements Of Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DiscontinuedOperationsAndAssetsAndLiabilitiesHeldForSaleComponentsOfDiscontinuedOperationsInCondensedConsolidatedStatementsOfIncomeDetails</Role>
      <ShortName>Discontinued Operations And Assets And Liabilities Held For Sale (Components Of Discontinued Operations In Condensed Consolidated Statements Of Income) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>2414403 - Disclosure - Discontinued Operations And Assets And Liabilities Held For Sale (Components Of Assets And Liabilities Held For Sale In Condensed Consolidated Balance Sheets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/DiscontinuedOperationsAndAssetsAndLiabilitiesHeldForSaleComponentsOfAssetsAndLiabilitiesHeldForSaleInCondensedConsolidatedBalanceSheetsDetails</Role>
      <ShortName>Discontinued Operations And Assets And Liabilities Held For Sale (Components Of Assets And Liabilities Held For Sale In Condensed Consolidated Balance Sheets) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>2415402 - Disclosure - Asset Retirement Obligations (AROs) (Reconciliation Of Changes In Asset Retirement Obligations) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/AssetRetirementObligationsArosReconciliationOfChangesInAssetRetirementObligationsDetails</Role>
      <ShortName>Asset Retirement Obligations (AROs) (Reconciliation Of Changes In Asset Retirement Obligations) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>2416402 - Disclosure - Related Parties (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/RelatedPartiesNarrativeDetails</Role>
      <ShortName>Related Parties (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>2416403 - Disclosure - Related Parties (Sales Credited And Purchases Billed) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/RelatedPartiesSalesCreditedAndPurchasesBilledDetails</Role>
      <ShortName>Related Parties (Sales Credited And Purchases Billed) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>2416404 - Disclosure - Related Parties (Corporate Services Billings) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/RelatedPartiesCorporateServicesBillingsDetails</Role>
      <ShortName>Related Parties (Corporate Services Billings) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>2416405 - Disclosure - Related Parties (Net Intercompany Payables) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/RelatedPartiesNetIntercompanyPayablesDetails</Role>
      <ShortName>Related Parties (Net Intercompany Payables) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>2416406 - Disclosure - Related Parties (Related Amounts Billed Between Parties) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/RelatedPartiesRelatedAmountsBilledBetweenPartiesDetails</Role>
      <ShortName>Related Parties (Related Amounts Billed Between Parties) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>2417402 - Disclosure - Earnings Per Share (Weighted Average Common Shares Outstanding) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.alliantenergy.com/role/EarningsPerShareWeightedAverageCommonSharesOutstandingDetails</Role>
      <ShortName>Earnings Per Share (Weighted Average Common Shares Outstanding) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element us-gaap_LossContingencyDamagesAwardedValue had a mix of decimals attribute values: -6 -5.</Log>
    <Log type="Info">Element us-gaap_ProceedsFromIssuanceOfLongTermDebt had a mix of decimals attribute values: -6 -5.</Log>
    <Log type="Info">'Monetary' elements on report '2406402 - Disclosure - Common Equity (Narrative) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - Condensed Consolidated Statements Of Income</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - Condensed Consolidated Balance Sheets</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Sep. 30, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 1002501 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - Condensed Consolidated Statements Of Cash Flows</Log>
  </Logs>
  <InputFiles>
    <File>lnt-20130930.xml</File>
    <File>lnt-20130930.xsd</File>
    <File>lnt-20130930_cal.xml</File>
    <File>lnt-20130930_def.xml</File>
    <File>lnt-20130930_lab.xml</File>
    <File>lnt-20130930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
