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Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph d(iv)(b)(i) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. 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This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Fair Value of Plan Assets3false 4us-gaap_DefinedBenefitPlanEstimatedFutureEmployerContributionsInCurrentFiscalYearus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse2040000020.4falsefalsefalse4truefalsefalse2040000020.4falsefalsefalse5truefalsefalse50000005.0falsefalsefalse6truefalsefalse50000005.0falsefalsefalse7truefalsefalse8000000.8falsefalsefalse8truefalsefalse8000000.8falsefalsefalsexbrli:monetaryItemTypemonetaryThe employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan in the current remaining fiscal period. 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This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920 false2Company ContributionfalseRetirement Benefits Activity (Details) (USD $)HundredThousandsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.pugetenergy.com/role/RetirementBenefitsActivityDetails84