2.2.0.7 false Basis of Presentation of Interim Consolidated Financial Statements (Details) (USD $) 009020 - Disclosure - Basis of Presentation of Interim Consolidated Financial Statements (Details) true false In Millions, except Share data false false 1 USD false false u000 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 u003 Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 u002 Standard http://www.xbrl.org/2003/instance shares xbrli 0 u001 Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ false 2 USD false false u000 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 u001 Standard http://www.xbrl.org/2003/instance pure xbrli 0 u002 Standard http://www.xbrl.org/2003/instance shares xbrli 0 u003 Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 $ 2 Notes To Financial Statements [Abstract] 0 str_NotesToFinancialStatementsAbstract str false na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 3 Ownership percentage in unconsolidated affiliate (in hundredths) 1 us-gaap_EquityMethodInvestmentOwnershipPercentage us-gaap true na instant No definition available. false false false false false false false false false false false label false 1 false false false false 0 0 false false false 2 false true false false 0.50 0.50 false false false us-types:percentItemType pure The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) false 4 Approval date of Reincorporation Merger 1 str_ReincorporationMergerDateOfApproval str false na duration Month, day and year when the reincorporation merger was approved, and the merger is effective. false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 May 18, 2010 May 18, 2010 false false false us-types:dateStringItemType normalizedstring Month, day and year when the reincorporation merger was approved, and the merger is effective. No authoritative reference available. false 5 Distribution date of tax-free, pro rata dividend to Questar shareholders 1 str_DistributionDateOfCapitalStockOfSubsidiariesToStockholders str false na duration Month, day and year when all of the shares of a subsidiaries' common stock held by the company was distributed to the... false false false false false false false false false false false terselabel false 1 false false false false 0 0 June 30, 2010 June 30, 2010 false false false 2 false false false false 0 0 false false false us-types:dateStringItemType normalizedstring Month, day and year when all of the shares of a subsidiaries' common stock held by the company was distributed to the company's shareholders as a tax-free, pro-rata dividend (the Spinoff). No authoritative reference available. false 6 Amount of noncash dividend 1 str_AmountOfNoncashDividend str false debit instant Amount of noncash dividend distributed to shareholders as a tax-free pro rata dividend (the Spinoff). false false false false false false false false false false false terselabel false 1 true true false false 2929700000 2929.7 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary Amount of noncash dividend distributed to shareholders as a tax-free pro rata dividend (the Spinoff). No authoritative reference available. false 7 Number of shares of QEP common stock received for each share of Questar common stock (in shares) 1 str_NumberOfSharesOfSubsidiaryCommonStockReceivedForEachShareOfParentCommonStock str false na instant Represents the number of shares of subsidiaries' common stock received by each shareholder, for each share of common stock... false false false false false false false false false false false terselabel false 1 false true false false 1 1 false false false 2 false false false false 0 0 false false false xbrli:sharesItemType shares Represents the number of shares of subsidiaries' common stock received by each shareholder, for each share of common stock held at the close of business on the record date, including fractional shares. No authoritative reference available. false 8 Equity contribution to QEP prior to Spinoff 1 str_AdvancesToUnconsolidatedAffiliate str false credit duration Amount of equity contributed to an affiliate prior to Spinoff. The affiliate is recorded as an equity method investment on... false false false false false false false false false false false terselabel false 1 true true false false 250000000 250.0 false false false 2 true true false false 250000000 250.0 false false false xbrli:monetaryItemType monetary Amount of equity contributed to an affiliate prior to Spinoff. The affiliate is recorded as an equity method investment on the Company's consolidated balance sheets. No authoritative reference available. false 2 7 false HundredThousands NoRounding UnKnown false true