Description of Business and Basis of Presentation	3 Months Ended
Description of Business and Basis of Presentation	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation Description of business — Murphy USA Inc. and its consolidated subsidiaries (“Murphy USA” or the “Company”) markets refined products through a network of retail gasoline stations and to unbranded wholesale customers. In addition, it operates non-fuel convenience stores in select markets in the Northeast. Murphy USA operates a chain of owned retail stations under the brand name of Murphy USA® which are almost all located in close proximity to Walmart stores in 25 states, markets gasoline and other products at standalone stations under the Murphy Express brand, and Quick Chek Corporation ("QuickChek") has convenience stores located in New Jersey and New York. At March 31, 2021, Murphy USA had a total of 1,660 Company stations of which 1,151 were Murphy USA, 353 were Murphy Express and 156 were QuickChek. Basis of Presentation — Murphy USA was incorporated in March 2013 and, in connection with its incorporation, Murphy USA issued 100 shares of common stock, par value $0.01 per share, to Murphy Oil Corporation (“Murphy Oil”) for $1.00. On August 30, 2013, Murphy USA was separated from Murphy Oil through the distribution of 100% of the common stock of Murphy USA to holders of Murphy Oil stock. Murphy USA Inc., Murphy Oil USA, and certain of its subsidiaries operate on a calendar year basis, while the subsidiary QuickChek uses a weekly retail calendar where each quarter has 13 weeks and its historical fiscal year end was the Friday nearest to October 31. For the Q1 2021 period, the results provided include the period from January 29, 2021 to April 2, 2021. The impact of the two additional days are immaterial to the overall consolidated results. In preparing the financial statements of Murphy USA in conformity with accounting principles generally accepted in the United States, management has made a number of estimates and assumptions related to the reporting of assets, liabilities, revenues, expenses and the disclosure of contingent assets and liabilities. Actual results may differ from these estimates. Accounting policies related to the acquisition of QuickChek — Business combinations — The purchase price of an acquisition is measured as the aggregate of the fair value of the consideration transferred. The purchase price is allocated to the fair values of the tangible and intangible assets acquired and liabilities assumed, with any excess recorded as goodwill. These fair value determinations require judgment and may involve the use of significant estimates and assumptions. The purchase price allocation may be provisional during a measurement period of up to one year to provide reasonable time to obtain the information necessary to identify and measure the assets acquired and liabilities assumed. Any such measurement period adjustments are recognized in the period in which the adjustment amount is determined. Transaction costs associated with the acquisition are expensed as incurred. Goodwill and intangible assets — Goodwill represents the excess of the aggregate of the consideration transferred over the net assets acquired and liabilities assumed and is tested annually for impairment, or more frequently if there are indicators of impairment. Acquired finite-lived intangible assets are amortized on a straight-line basis over their estimated useful lives, and are reviewed for impairment when events or circumstances indicate that the asset group to which the intangible assets belong might be impaired. The Company revises the estimated remaining useful life of these assets when events or changes in circumstances warrant a revision. If the Company revises the useful life, the unamortized balance is amortized over the use life on a prospective basis. Indefinite-lived intangibles are tested annually for impairment, or more often if indicators warrant. Interim Financial Information — The interim period financial information presented in these consolidated financial statements is unaudited and includes all known accruals and adjustments, in the opinion of management, necessary for a fair presentation of the consolidated financial position of Murphy USA and its results of operations and cash flows for the periods presented. All such adjustments are of a normal and recurring nature. These interim consolidated financial statements should be read together with our audited financial statements for the years ended December 31, 2020, 2019 and 2018, included in our Annual Report on Form 10-K (File No. 001-35914), as filed with the Securities and Exchange Commission under the Securities Exchange Act of 1934 on February 19, 2021. Recently Issued Accounting Standards— In March 2020, the FASB issued ASU 2020-04, "Reference Rate Reform (Topic 848) - Facilitation of the Effects of Reference Rate Reform on Financial Reporting". This standard included optional guidance for a limited period of time to help ease the burden in accounting for the effects of reference rate reform. The new standard is effective for all entities through December 31, 2022. The Company does not expect the adoption of this standard to have a material impact on the Company's consolidated financial statements.