<?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>HtmlAndXml</ReportFormat>
  <ContextCount>345</ContextCount>
  <ElementCount>272</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>61</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>12</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.pugetenergy.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
      <XmlFileName>R1.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
      <XmlFileName>R2.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002000 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <XmlFileName>R3.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002501 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/ConsolidatedStatementsOfComprehensiveIncomeParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical)</ShortName>
      <XmlFileName>R4.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <XmlFileName>R5.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1003501 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <XmlFileName>R6.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1005000 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <XmlFileName>R7.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <XmlFileName>R8.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - New Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/NewAccountingPronouncements</Role>
      <ShortName>New Accounting Pronouncements</ShortName>
      <XmlFileName>R9.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Accounting for Derivative Instruments and Hedging Activities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccountingForDerivativeInstrumentsAndHedgingActivities</Role>
      <ShortName>Accounting for Derivative Instruments and Hedging Activities</ShortName>
      <XmlFileName>R10.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <XmlFileName>R11.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Retirement Benefits</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/RetirementBenefits</Role>
      <ShortName>Retirement Benefits</ShortName>
      <XmlFileName>R12.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Regulation and Rates</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/RegulationAndRates</Role>
      <ShortName>Regulation and Rates</ShortName>
      <XmlFileName>R13.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Litigation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/Litigation</Role>
      <ShortName>Litigation</ShortName>
      <XmlFileName>R14.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Accumulated Other Comprehensive Income (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.pugetenergy.com/role/AccumulatedOtherComprehensiveIncomeNotes</Role>
      <ShortName>Accumulated Other Comprehensive Income (Notes)</ShortName>
      <XmlFileName>R15.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Other</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/Other</Role>
      <ShortName>Other</ShortName>
      <XmlFileName>R16.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/SummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <XmlFileName>R17.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2301302 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/SummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
      <XmlFileName>R18.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Accounting for Derivative Instruments and Hedging Activities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccountingForDerivativeInstrumentsAndHedgingActivitiesTables</Role>
      <ShortName>Accounting for Derivative Instruments and Hedging Activities (Tables)</ShortName>
      <XmlFileName>R19.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <XmlFileName>R20.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - Retirement Benefits (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/RetirementBenefitsTables</Role>
      <ShortName>Retirement Benefits (Tables)</ShortName>
      <XmlFileName>R21.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - Accumulated Other Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccumulatedOtherComprehensiveIncomeTables</Role>
      <ShortName>Accumulated Other Comprehensive Income (Tables)</ShortName>
      <XmlFileName>R22.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2401403 - Disclosure - Summary of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/SummaryOfSignificantAccountingPoliciesDetails</Role>
      <ShortName>Summary of Significant Accounting Policies (Details)</ShortName>
      <XmlFileName>R23.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2401404 - Disclosure - Summary of Significant Accounting Policies Cash Flow Restatements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/SummaryOfSignificantAccountingPoliciesCashFlowRestatementsDetails</Role>
      <ShortName>Summary of Significant Accounting Policies Cash Flow Restatements (Details)</ShortName>
      <XmlFileName>R24.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Accounting for Derivative Instruments and Hedging Activities Derivative Activity and Notional Amounts (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccountingForDerivativeInstrumentsAndHedgingActivitiesDerivativeActivityAndNotionalAmountsDetails</Role>
      <ShortName>Accounting for Derivative Instruments and Hedging Activities Derivative Activity and Notional Amounts (Details)</ShortName>
      <XmlFileName>R25.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - Accounting for Derivative Instruments and Hedging Activities Derivative Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccountingForDerivativeInstrumentsAndHedgingActivitiesDerivativeAssetsAndLiabilitiesDetails</Role>
      <ShortName>Accounting for Derivative Instruments and Hedging Activities Derivative Assets and Liabilities (Details)</ShortName>
      <XmlFileName>R26.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2403404 - Disclosure - Accounting for Derivative Instruments and Hedging Activities Net Amount of Derivatives Reported in the Statement of Financial Position (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccountingForDerivativeInstrumentsAndHedgingActivitiesNetAmountOfDerivativesReportedInStatementOfFinancialPositionDetails</Role>
      <ShortName>Accounting for Derivative Instruments and Hedging Activities Net Amount of Derivatives Reported in the Statement of Financial Position (Details)</ShortName>
      <XmlFileName>R27.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2403405 - Disclosure - Accounting for Derivative Instruments and Hedging Activities Recognized in Statement of Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccountingForDerivativeInstrumentsAndHedgingActivitiesRecognizedInStatementOfIncomeDetails</Role>
      <ShortName>Accounting for Derivative Instruments and Hedging Activities Recognized in Statement of Income (Details)</ShortName>
      <XmlFileName>R28.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2403406 - Disclosure - Accounting for Derivative Instruments and Hedging Activities Recognized in Other Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccountingForDerivativeInstrumentsAndHedgingActivitiesRecognizedInOtherComprehensiveIncomeDetails</Role>
      <ShortName>Accounting for Derivative Instruments and Hedging Activities Recognized in Other Comprehensive Income (Details)</ShortName>
      <XmlFileName>R29.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2403407 - Disclosure - Accounting for Derivative Instruments and Hedging Activities Contractual Contingent Liability (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccountingForDerivativeInstrumentsAndHedgingActivitiesContractualContingentLiabilityDetails</Role>
      <ShortName>Accounting for Derivative Instruments and Hedging Activities Contractual Contingent Liability (Details)</ShortName>
      <XmlFileName>R30.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Fair Value Measurements Carrying Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/FairValueMeasurementsCarryingValueDetails</Role>
      <ShortName>Fair Value Measurements Carrying Value (Details)</ShortName>
      <XmlFileName>R31.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Fair Value Measurements Debt at at Carrying and Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/FairValueMeasurementsDebtAtAtCarryingAndFairValueDetails</Role>
      <ShortName>Fair Value Measurements Debt at at Carrying and Fair Value (Details)</ShortName>
      <XmlFileName>R32.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - Fair Value Measurements Assets and Liabilities Measured on Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/FairValueMeasurementsAssetsAndLiabilitiesMeasuredOnRecurringBasisDetails</Role>
      <ShortName>Fair Value Measurements Assets and Liabilities Measured on Recurring Basis (Details)</ShortName>
      <XmlFileName>R33.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2404405 - Disclosure - Fair Value Measurements Valuation Technicques for Measurement with Unobservable Inputs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/FairValueMeasurementsValuationTechnicquesForMeasurementWithUnobservableInputsDetails</Role>
      <ShortName>Fair Value Measurements Valuation Technicques for Measurement with Unobservable Inputs (Details)</ShortName>
      <XmlFileName>R34.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2404406 - Disclosure - Fair Value Measurements Unobservable Input Reconciliation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/FairValueMeasurementsUnobservableInputReconciliationDetails</Role>
      <ShortName>Fair Value Measurements Unobservable Input Reconciliation (Details)</ShortName>
      <XmlFileName>R35.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - Retirement Benefits Net Periodic Benefit Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/RetirementBenefitsNetPeriodicBenefitCostDetails</Role>
      <ShortName>Retirement Benefits Net Periodic Benefit Cost (Details)</ShortName>
      <XmlFileName>R36.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2406403 - Disclosure - Retirement Benefits Change in Net Benefit Obligation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/RetirementBenefitsChangeInNetBenefitObligationDetails</Role>
      <ShortName>Retirement Benefits Change in Net Benefit Obligation (Details)</ShortName>
      <XmlFileName>R37.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2406404 - Disclosure - Retirement Benefits Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/RetirementBenefitsActivityDetails</Role>
      <ShortName>Retirement Benefits Activity (Details)</ShortName>
      <XmlFileName>R38.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2407401 - Disclosure - Regulation and Rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/RegulationAndRatesDetails</Role>
      <ShortName>Regulation and Rates (Details)</ShortName>
      <XmlFileName>R39.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2408401 - Disclosure - Litigation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/LitigationDetails</Role>
      <ShortName>Litigation (Details)</ShortName>
      <XmlFileName>R40.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Accumulated Other Comprehensive Income - Changes by Component (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccumulatedOtherComprehensiveIncomeChangesByComponentDetails</Role>
      <ShortName>Accumulated Other Comprehensive Income - Changes by Component (Details)</ShortName>
      <XmlFileName>R41.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - Accumulated Other Comprehensive Income - Reclassification Location (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/AccumulatedOtherComprehensiveIncomeReclassificationLocationDetails</Role>
      <ShortName>Accumulated Other Comprehensive Income - Reclassification Location (Details)</ShortName>
      <XmlFileName>R42.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2410401 - Disclosure - Other Jefferson County Public Utility District (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/OtherJeffersonCountyPublicUtilityDistrictDetails</Role>
      <ShortName>Other Jefferson County Public Utility District (Details)</ShortName>
      <XmlFileName>R43.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Other Bond Issuances (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pugetenergy.com/role/OtherBondIssuancesDetails</Role>
      <ShortName>Other Bond Issuances (Details)</ShortName>
      <XmlFileName>R44.xml</XmlFileName>
    </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 psd_PublicUtilitiesRateCaseApprovedEffectiveWeightedCostOfCapital had a mix of decimals attribute values: 3 4.</Log>
    <Log type="Info">'Monetary' elements on report '2403403 - Disclosure - Accounting for Derivative Instruments and Hedging Activities Derivative Assets and Liabilities (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2403405 - Disclosure - Accounting for Derivative Instruments and Hedging Activities Recognized in Statement of Income (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2403406 - Disclosure - Accounting for Derivative Instruments and Hedging Activities Recognized in Other Comprehensive Income (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2404404 - Disclosure - Fair Value Measurements Assets and Liabilities Measured on Recurring Basis (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2404405 - Disclosure - Fair Value Measurements Valuation Technicques for Measurement with Unobservable Inputs (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2404406 - Disclosure - Fair Value Measurements Unobservable Input Reconciliation (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - CONSOLIDATED STATEMENTS OF INCOME</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</Log>
    <Log type="Info">Process Flow-Through: 1002501 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - CONSOLIDATED BALANCE SHEETS</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Mar. 31, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Jun. 30, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 1003501 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1005000 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</Log>
    <Log type="Info">	Process Flow-Through: Removing column '12 Months Ended
Dec. 31, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '12 Months Ended
Dec. 31, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '12 Months Ended
Dec. 31, 2010'</Log>
  </Logs>
  <InputFiles>
    <File>psd-20130630.xml</File>
    <File>psd-20130630.xsd</File>
    <File>psd-20130630_cal.xml</File>
    <File>psd-20130630_def.xml</File>
    <File>psd-20130630_lab.xml</File>
    <File>psd-20130630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
