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Excludes transportation, gathering and storage costs.No definition available.false2Gas purchases8false 5str_OperatorServiceFeestr_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse7420000074.2USD$falsefalsefalse2truefalsefalse6950000069.5USD$falsefalsefalse3truefalsefalse147000000147.0USD$falsefalsefalse4truefalsefalse135200000135.2USD$falsefalsefalse5truefalsefalse285800000285.8USD$falsefalsefalse6truefalsefalse266700000266.7USD$falsefalsefalsexbrli:monetaryItemTypemonetaryOperator service fee charged to Questar Gas by Wexpro for the development and operation of cost-of-service natural gas reserves.No definition available.false2Operator service fee9false 5str_TransportationAndStoragestr_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1810000018.1USD$falsefalsefalse2truefalsefalse1890000018.9USD$falsefalsefalse3truefalsefalse4010000040.1USD$falsefalsefalse4truefalsefalse3950000039.5USD$falsefalsefalse5truefalsefalse8020000080.2USD$falsefalsefalse6truefalsefalse7820000078.2USD$falsefalsefalsexbrli:monetaryItemTypemonetaryNatural gas transportation and storage costs, predominantly consists of amounts charged to Questar Gas by Questar Pipeline.No definition available.false2Transportation and storage10false 5str_Gatheringstr_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse45000004.5USD$falsefalsefalse2truefalsefalse51000005.1USD$falsefalsefalse3truefalsefalse91000009.1USD$falsefalsefalse4truefalsefalse1120000011.2USD$falsefalsefalse5truefalsefalse1840000018.4USD$falsefalsefalse6truefalsefalse2410000024.1USD$falsefalsefalsexbrli:monetaryItemTypemonetaryNatural gas gathering costs charged by third parties.No definition available.false2Gathering11false 5str_Royaltiesstr_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1030000010.3USD$falsefalsefalse2truefalsefalse62000006.2USD$falsefalsefalse3truefalsefalse2140000021.4USD$falsefalsefalse4truefalsefalse1640000016.4USD$falsefalsefalse5truefalsefalse3700000037.0USD$falsefalsefalse6truefalsefalse3740000037.4USD$falsefalsefalsexbrli:monetaryItemTypemonetaryPortion of gas purchase costs that represents amounts paid to Wexpro to reimburse them for royalties on natural gas and other products. Royalties are billed to Questar Gas by Wexpro separate from the operator service fee.No definition available.false2Royalties12false 5str_StorageInjectionWithdrawalNetstr_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-9600000-9.6USD$falsefalsefalse2truefalsefalse-16500000-16.5USD$falsefalsefalse3truefalsefalse1920000019.2USD$falsefalsefalse4truefalsefalse1090000010.9USD$falsefalsefalse5truefalsefalse1020000010.2USD$falsefalsefalse6truefalsefalse-10700000-10.7USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents the offset to inventory entries when natural gas is physically injected into or withdrawn from storage facilities. 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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 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 false2Purchased-gas account adjustment14false 5str_Othergascostcomponentsstr_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse14000001.4USD$falsefalsefalse2truefalsefalse13000001.3USD$falsefalsefalse3truefalsefalse27000002.7USD$falsefalsefalse4truefalsefalse26000002.6USD$falsefalsefalse5truefalsefalse51000005.1USD$falsefalsefalse6truefalsefalse51000005.1USD$falsefalsefalsexbrli:monetaryItemTypemonetaryOther miscellaneous components of Questar Gas cost of natural gas sold.No definition available.false2Other15false 5us-gaap_CostOfDomesticRegulatedGasRevenueus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse8350000083.5USD$falsefalsefalse2truefalsefalse7550000075.5USD$falsefalsefalse3truefalsefalse374100000374.1USD$falsefalsefalse4truefalsefalse311700000311.7USD$falsefalsefalse5truefalsefalse595700000595.7USD$falsefalsefalse6truefalsefalse558900000558.9USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cost of generation, transmission, and distribution of [natural] gas, which are regulated by a federal, state, or local government or agency.No definition available.true2Total Questar Gas cost of natural gas sold16false 5str_CostofDomesticRegulatedGasRevenueAffiliatedCompaniesstr_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-91800000-91.8USD$falsefalsefalse2truefalsefalse-87700000-87.7USD$falsefalsefalse3truefalsefalse-183900000-183.9USD$falsefalsefalse4truefalsefalse-171700000-171.7USD$falsefalsefalse5truefalsefalse-359900000-359.9USD$falsefalsefalse6truefalsefalse-340000000-340.0USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of oil and gas purchased from affiliated companies during the reporting period.No definition available.false2Elimination of Questar Gas cost of natural gas sold - affiliated parties17false 5str_CostOfPurchasedOilAndGasUnaffiliatedPartiesstr_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-8300000-8.3USD$falsefalsefalse2truefalsefalse-12200000-12.2USD$falsefalsefalse3truefalsefalse190200000190.2USD$falsefalsefalse4truefalsefalse140000000140.0USD$falsefalsefalse5truefalsefalse235800000235.8USD$falsefalsefalse6truefalsefalse218900000218.9USD$falsefalsefalsexbrli:monetaryItemTypemonetaryCost of oil and gas purchased from unaffiliated parties during the reporting period.No definition available.false2Total Questar Gas cost of natural gas sold - unaffiliated parties18false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse13false USDtruefalse$D2013Q2_dei_LegalEntityAxis_str_QuestarPipelineMemberhttp://www.sec.gov/CIK0000751652duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseQuestar Pipeline [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldistr_QuestarPipelineMemberdei_LegalEntityAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Questar Pipeline [Member]19true 4us-gaap_CostOfGoodsAndServicesSoldAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Cost of Sales [Abstract]20false 5us-gaap_CostOfGoodsAndServicesSoldus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse10000001.0USD$falsetruefalse2truefalsefalse7000000.7USD$falsetruefalse3truefalsefalse22000002.2USD$falsetruefalse4truefalsefalse12000001.2USD$falsetruefalse5truefalsefalse77000007.7USD$falsetruefalse6truefalsefalse27000002.7USD$falsetruefalsexbrli:monetaryItemTypemonetaryThe aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 2 -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 210.5-03.2(a),(d)) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 false2Total Questar Pipeline cost of salesfalseBasis of Presentation of Interim Financial Statements (Details) (USD $)HundredThousandsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.questar.com/role/BasisOfPresentationOfInterimFinancialStatementsDetails620