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

No definition available.

Name:	str_AverageAnnualRateOfReturnAfterTax
Namespace Prefix:	str_
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

Net investment base of the subsidiary.

No definition available.

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:	us-types: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:	us-types: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:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

Wexpro Agreement (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Agreement [Line Items]
Percentage of Wexpro retention (in hundredths)	46.00%
Wexpro's net investment base (in millions)	$ 474.4	$ 456.6	$ 431.9
Average annual rate of return (after tax) (in hundredths)	20.00%	20.00%	20.10%
Gas-development drilling [Member]
Agreement [Line Items]
Percentage of Wexpro after tax rate of return (in hundredths)	20.50%
Natural Gas operations [Member]
Agreement [Line Items]
Percentage of Wexpro after tax rate of return (in hundredths)	12.50%
Developmental Oil Drilling [Member]
Agreement [Line Items]
Percentage of Wexpro after tax rate of return (in hundredths)	17.50%
Percentage of Wexpro retention (in hundredths)	46.00%
Percentage of Questar Gas retention (in hundredths)	54.00%
Oil Income Sharing Amounts Per Agreement	$ 3.3	$ 1.1	$ 1.0
Crude Oil Production [Member]
Agreement [Line Items]
Percentage of Wexpro after tax rate of return (in hundredths)	12.50%
Percentage of Wexpro retention (in hundredths)	46.00%