Name:	str_AgreementLineItems
Namespace Prefix:	str_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The after tax average rate of return from operations under the agreement.

No definition available.

Name:	str_AverageAnnualRateOfReturnAfterTax
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Canyon Creek Acquisition Specified Questar Gas Supply Percetange by 2020

No definition available.

Name:	str_CanyonCreekAcquisitionSpecifiedQuestarGasSupplyPercetangeby2020
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Max percentage of development drilling program costs

No definition available.

Name:	str_Maxpercentageofdevelopmentdrillingprogramcosts
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Net investment base of the subsidiary.

No definition available.

Name:	str_NetInvestmentBase
Namespace Prefix:	str_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of operating income received by subsidiary from operations as outlined by the agreement.

No definition available.

Name:	str_OilIncomeSharingAmountsPerAgreement
Namespace Prefix:	str_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The percentage of after-tax return allowed to subsidiary from operations as outlined by the agreement.

No definition available.

Name:	str_PercentageOfAfterTaxRateOfReturn
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage of operating income retained by the subsidiary from operations as outlined by agreement.

No definition available.

Name:	str_PercentageOfOperatingIncomeRetention
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage of operating income retained by subsidiary from operations as outlined by agreement that are other than Wexpro.

No definition available.

Name:	str_PercentageOfOperatingIncomeRetentionGas
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The rate-of-return premium relative to a group of regulated companies' returns allowed to subsidiary from operations as outlined by the agreement.

No definition available.

Name:	str_PercentageofPremiumAddedtoBaseAfterTaxRateofReturn
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of dry-hole and non-commercial well costs retention

No definition available.

Name:	str_Percentageofdryholeandnoncommercialwellcostsretention
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Stipulation savings for price differential

No definition available.

Name:	str_Stipulationsavingsforpricedifferential
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

To the extent the Questar Gas supply provided by Wexpro I properties plus Trail acquisition properties exceeds 65%, special treatment is required such that Questar Gas customers pay the lower of Questar Gas purchased-gas price or Wexpro cost-of-service price on the incremental volumes.

No definition available.

Name:	str_TrailAcquisitionSpecifiedQuestarGasSupplyPercentage
Namespace Prefix:	str_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Name:	str_MajorProvisionsOfAgreementAxis=str_GasDevelopmentDrillingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	str_MajorProvisionsOfAgreementAxis=str_NaturalGasOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	str_MajorProvisionsOfAgreementAxis=str_DevelopmentalOilDrillingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	str_MajorProvisionsOfAgreementAxis=str_CrudeOilProductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	str_MajorProvisionsOfAgreementAxis=str_AcquirednaturalgasproductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_LegalEntityAxis=str_WexproMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: