1.0.0.3 false Asset Retirement Obligations (ARO) false 1 $ false false u000 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 u001 Standard http://www.xbrl.org/2003/instance shares xbrli 0 u002 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 string No definition available. false false false false false true false false false 1 false false 0 0 false false No definition available. false 3 Asset Retirement Obligations 1 us-gaap_CapitalizedCostsRelatingToOilAndGasProducingActivitiesDisclosureTextBlock us-gaap true na duration string No definition available. false false false false false false false false false 1 false false 0 0 Note 8 - Asset Retirement Obligations Questar records asset retirement obligations (ARO) when there are legal obligations associated with the retirement of tangible long-lived assets. At Questar, ARO apply primarily to abandonment costs associated with gas and oil wells, production facilities and certain other properties. The fair value of retirement costs are estimated by Company personnel based on abandonment costs of similar properties (Level 3 inputs under fair-value measurement provisions) available to field operations and depreciated over the life of the related assets. Revisions to ARO estimates result from changes in expected cash flows or material changes in estimated retirement costs. Income or expense resulting from the settlement of ARO liabilities is included in net gain or (loss) from asset sales on the Consolidated Statements of Income. The ARO liability is adjusted to present value each period through an accretion calculation using a credit-adjusted risk-free interest rate. Changes in ARO were as follows: Level 3 fair value 2009 2008 (in millions) ARO liability at Jan. 1, $175.6 $149.1 Accretion 8.2 7.2 Liabilities incurred 2.3 13.9 Revisions 2.4 1.5 Liabilities settled (2.4) (2.1)ARO liability at Sept. 30, $186.1 $169.6 Wexpro collects from Questar Gas and deposits in trust certain funds related to estimated ARO costs. The funds are used to satisfy retirement obligations as the properties are abandoned and recorded in other noncurrent assets on the Consolidated Balance Sheets. Trust funds are invested primarily in a money-market account with a balance of $11.2 million at September 30, 2009. The fair value of Wexpro's trust is based on asset summary statements provided by the bank holding the trust and considered Level 2 fair value measurement. Note 8 - Asset Retirement Obligations Questar records asset retirement obligations (ARO) when there are legal obligations associated with the retirement of false false No definition available. No authoritative reference available. false false 1 2 false UnKnown UnKnown UnKnown false true