3.4.0.3 html 123 203 1 true 26 0 false 6 false false R1.htm 0001000 - Document - Document And Entity Information Sheet http://www.questar.com/role/DocumentAndEntityInformation Document And Entity Information Cover 1 false false R2.htm 1001000 - Statement - CONSOLIDATED STATEMENTS OF INCOME Sheet http://www.questar.com/role/ConsolidatedStatementsOfIncome CONSOLIDATED STATEMENTS OF INCOME Statements 2 false false R3.htm 1002000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Sheet http://www.questar.com/role/CondensedConsolidatedStatementsOfComprehensiveIncome CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Statements 3 false false R4.htm 1004000 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS Sheet http://www.questar.com/role/CondensedConsolidatedBalanceSheets CONDENSED CONSOLIDATED BALANCE SHEETS Statements 4 false false R5.htm 1005000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS Sheet http://www.questar.com/role/CondensedConsolidatedStatementsOfCashFlows CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS Statements 5 false false R6.htm 2101100 - Disclosure - Nature of Business Sheet http://www.questar.com/role/NatureOfBusiness Nature of Business Notes 6 false false R7.htm 2102100 - Disclosure - Proposed Merger with Dominion Resources Sheet http://www.questar.com/role/ProposedMergerWithDominionResources Proposed Merger with Dominion Resources Notes 7 false false R8.htm 2103100 - Disclosure - Basis of Presentation of Interim Financial Statements Sheet http://www.questar.com/role/BasisOfPresentationOfInterimFinancialStatements Basis of Presentation of Interim Financial Statements Notes 8 false false R9.htm 2104100 - Disclosure - Earnings Per Share Sheet http://www.questar.com/role/EarningsPerShare Earnings Per Share Notes 9 false false R10.htm 2105100 - Disclosure - Accumulated Other Comprehensive Income Sheet http://www.questar.com/role/AccumulatedOtherComprehensiveIncome Accumulated Other Comprehensive Income Notes 10 false false R11.htm 2106100 - Disclosure - Asset Retirement Obligations Sheet http://www.questar.com/role/AssetRetirementObligations Asset Retirement Obligations Notes 11 false false R12.htm 2107100 - Disclosure - Fair Value Measurements Sheet http://www.questar.com/role/FairValueMeasurements Fair Value Measurements Notes 12 false false R13.htm 2109100 - Disclosure - Derivatives and Hedging Sheet http://www.questar.com/role/DerivativesAndHedging Derivatives and Hedging Notes 13 false false R14.htm 2110100 - Disclosure - Operations by Line of Business Sheet http://www.questar.com/role/OperationsByLineOfBusiness Operations by Line of Business Notes 14 false false R15.htm 2111100 - Disclosure - Employee Benefits Sheet http://www.questar.com/role/EmployeeBenefits Employee Benefits Notes 15 false false R16.htm 2112100 - Disclosure - Contingencies Sheet http://www.questar.com/role/Contingencies Contingencies Notes 16 false false R17.htm 2114100 - Disclosure - Asset Impairments Sheet http://www.questar.com/role/AssetImpairments Asset Impairments Notes 17 false false R18.htm 2115100 - Disclosure - Accounting Developments Sheet http://www.questar.com/role/AccountingDevelopments Accounting Developments Notes 18 false false R19.htm 2203201 - Disclosure - Basis of Presentation of Interim Financial Statements (Policies) Sheet http://www.questar.com/role/BasisOfPresentationOfInterimFinancialStatementsPolicies Basis of Presentation of Interim Financial Statements (Policies) Policies http://www.questar.com/role/AccountingDevelopments 19 false false R20.htm 2303302 - Disclosure - Basis of Presentation of Interim Financial Statements (Tables) Sheet http://www.questar.com/role/BasisOfPresentationOfInterimFinancialStatementsTables Basis of Presentation of Interim Financial Statements (Tables) Tables http://www.questar.com/role/BasisOfPresentationOfInterimFinancialStatements 20 false false R21.htm 2304301 - Disclosure - Earnings Per Share (Tables) Sheet http://www.questar.com/role/EarningsPerShareTables Earnings Per Share (Tables) Tables http://www.questar.com/role/EarningsPerShare 21 false false R22.htm 2305301 - Disclosure - Accumulated Other Comprehensive Income (Tables) Sheet http://www.questar.com/role/AccumulatedOtherComprehensiveIncomeTables Accumulated Other Comprehensive Income (Tables) Tables http://www.questar.com/role/AccumulatedOtherComprehensiveIncome 22 false false R23.htm 2306301 - Disclosure - Asset Retirement Obligations (Tables) Sheet http://www.questar.com/role/AssetRetirementObligationsTables Asset Retirement Obligations (Tables) Tables http://www.questar.com/role/AssetRetirementObligations 23 false false R24.htm 2307301 - Disclosure - Fair Value Measurements (Tables) Sheet http://www.questar.com/role/FairValueMeasurementsTables Fair Value Measurements (Tables) Tables http://www.questar.com/role/FairValueMeasurements 24 false false R25.htm 2310301 - Disclosure - Operations by Line of Business (Tables) Sheet http://www.questar.com/role/OperationsByLineOfBusinessTables Operations by Line of Business (Tables) Tables http://www.questar.com/role/OperationsByLineOfBusiness 25 false false R26.htm 2311301 - Disclosure - Employee Benefits (Tables) Sheet http://www.questar.com/role/EmployeeBenefitsTables Employee Benefits (Tables) Tables http://www.questar.com/role/EmployeeBenefits 26 false false R27.htm 2401401 - Disclosure - Nature of Business (Details) Sheet http://www.questar.com/role/NatureOfBusinessDetails Nature of Business (Details) Details http://www.questar.com/role/NatureOfBusiness 27 false false R28.htm 2402401 - Disclosure - Proposed Merger with Dominion Resources (Details) Sheet http://www.questar.com/role/ProposedMergerWithDominionResourcesDetails Proposed Merger with Dominion Resources (Details) Details http://www.questar.com/role/ProposedMergerWithDominionResources 28 false false R29.htm 2403403 - Disclosure - Basis of Presentation of Interim Financial Statements (Details) Sheet http://www.questar.com/role/BasisOfPresentationOfInterimFinancialStatementsDetails Basis of Presentation of Interim Financial Statements (Details) Details http://www.questar.com/role/BasisOfPresentationOfInterimFinancialStatementsTables 29 false false R30.htm 2404402 - Disclosure - Earnings Per Share (Details) Sheet http://www.questar.com/role/EarningsPerShareDetails Earnings Per Share (Details) Details http://www.questar.com/role/EarningsPerShareTables 30 false false R31.htm 2405402 - Disclosure - Accumulated Other Comprehensive Income (Details) Sheet http://www.questar.com/role/AccumulatedOtherComprehensiveIncomeDetails Accumulated Other Comprehensive Income (Details) Details http://www.questar.com/role/AccumulatedOtherComprehensiveIncomeTables 31 false false R32.htm 2406402 - Disclosure - Asset Retirement Obligations (Details) Sheet http://www.questar.com/role/AssetRetirementObligationsDetails Asset Retirement Obligations (Details) Details http://www.questar.com/role/AssetRetirementObligationsTables 32 false false R33.htm 2407402 - Disclosure - Fair Value Measurements (Details) Sheet http://www.questar.com/role/FairValueMeasurementsDetails Fair Value Measurements (Details) Details http://www.questar.com/role/FairValueMeasurementsTables 33 false false R34.htm 2409401 - Disclosure - Derivatives and Hedging (Details) Sheet http://www.questar.com/role/DerivativesAndHedgingDetails Derivatives and Hedging (Details) Details http://www.questar.com/role/DerivativesAndHedging 34 false false R35.htm 2410402 - Disclosure - Operations by Line of Business (Details) Sheet http://www.questar.com/role/OperationsByLineOfBusinessDetails Operations by Line of Business (Details) Details http://www.questar.com/role/OperationsByLineOfBusinessTables 35 false false R36.htm 2411402 - Disclosure - Employee Benefits (Details) Sheet http://www.questar.com/role/EmployeeBenefitsDetails Employee Benefits (Details) Details http://www.questar.com/role/EmployeeBenefitsTables 36 false false R37.htm 2412401 - Disclosure - Contingencies (Details) Sheet http://www.questar.com/role/ContingenciesDetails Contingencies (Details) Details http://www.questar.com/role/Contingencies 37 false false R38.htm 2414401 - Disclosure - Asset Impairments (Details) Sheet http://www.questar.com/role/AssetImpairmentsDetails Asset Impairments (Details) Details http://www.questar.com/role/AssetImpairments 38 false false All Reports Book All Reports str-20160331.xml str-20160331.xsd str-20160331_cal.xml str-20160331_def.xml str-20160331_lab.xml str-20160331_pre.xml true true