Summary of Significant Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Feb. 16, 2020
Accounting Policies [Abstract]
Summary of Significant Policies	Note 1—Summary of Significant Accounting Policies Description of Business Costco Wholesale Corporation (Costco or the Company), a Washington corporation, and its subsidiaries operate membership warehouses based on the concept that offering members low prices on a limited selection of nationally branded and private-label products in a wide range of merchandise categories will produce high sales volumes and rapid inventory turnover. For the period ended February 16, 2020, Costco operated 785 warehouses worldwide: 546 in the United States (U.S.) located in 44 states, Washington, D.C., and Puerto Rico, 100 in Canada, 39 in Mexico, 29 in the United Kingdom (U.K.), 26 in Japan, 16 in Korea, 13 in Taiwan, 11 in Australia, two in Spain, and one each in Iceland, France and China. The Company operates e-commerce websites in the U.S., Canada, Mexico, U.K., Korea, Taiwan, Japan, and Australia. Basis of Presentation The condensed consolidated financial statements include the accounts of Costco, its wholly owned subsidiaries, and subsidiaries in which it has a controlling interest. The Company reports noncontrolling interests in consolidated entities as a component of equity separate from the Company’s equity. All material intercompany transactions between and among the Company and its consolidated subsidiaries have been eliminated in consolidation. The Company’s net income excludes income attributable to the noncontrolling interest in Taiwan. Unless otherwise noted, references to net income relate to net income attributable to Costco. These unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q for interim financial reporting pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). While these statements reflect all normal recurring adjustments that are, in the opinion of management, necessary for fair presentation of the results of the interim period, they do not include all of the information and footnotes required by U.S. generally accepted accounting principles (U.S. GAAP) for complete financial statements. Therefore, the interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company's Annual Report filed on Form 10-K for the fiscal year ended September 1, 2019. Fiscal Year End The Company operates on a 52/53 week fiscal year basis, with the fiscal year ending on the Sunday closest to August 31. Fiscal 2020 is a 52-week year ending on August 30, 2020. References to the second quarter of 2020 and 2019 relate to the 12-week fiscal quarters ended February 16, 2020, and February 17, 2019, respectively. References to the first half of 2020 and 2019 relate to the 24 weeks ended February 16, 2020, and February 17, 2019, respectively. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates and assumptions. Leases The Company leases land and/or buildings at warehouses and certain other office and distribution facilities. Leases generally contain one or more of the following options, which the Company can exercise at the end of the initial term: (a) renew the lease for a defined number of years at the then-fair market rental rate or rate stipulated in the lease agreement; (b) purchase the property at the then-fair market value; or (c) a right of first refusal in the event of a third-party offer. Some leases include free-rent periods and step-rent provisions, which are recognized on a straight-line basis over the original term of the lease and any extension options that the Company is reasonably certain to exercise from the date the Company has control of the property. Certain leases provide for periodic rent increases based on price indices or the greater of minimum guaranteed amounts or sales volume. Our leases do not contain any material residual value guarantees or material restrictive covenants. The Company determines at inception whether a contract is or contains a lease. The Company initially records right-of-use (ROU) assets and lease obligations for its finance and operating leases based on the discounted future minimum lease payments over the term. As the rate implicit in the Company’s leases is not easily determinable, the present value of the sum of the lease payments is calculated by using the Company’s incremental borrowing rate. The rate is determined using a portfolio approach based on the rate of interest the Company would pay to borrow an amount equal to the lease payments on a collateralized basis over a similar term. The Company uses quoted interest rates from financial institutions to derive the incremental borrowing rate. The lease term is defined as the noncancelable period of the lease plus any options to extend when it is reasonably certain that the Company will exercise the option. Recent Accounting Pronouncements Adopted In February 2016, the Financial Accounting Standards Board (FASB) issued ASU 2016-02 - Leases (ASC 842), which required recognition on the balance sheet for the rights and obligations created by leases with terms greater than 12 months. The Company adopted ASC 842 using the modified retrospective transition method and elected to use the effective date of September 2, 2019, as the date of initial application. Consequently, the comparative periods presented continue to be in accordance with ASC 840, Leases, previously in effect. The Company elected the package of practical expedients permitted under the transition guidance, allowing the Company to carry forward conclusions related to: (a) whether expired or existing contracts contain leases; (b) lease classification; and (c) initial direct costs for existing leases. The Company has elected not to record operating lease right-of-use assets or lease liabilities associated with leases with durations of 12 months or less. Lastly, the Company elected the practical expedient allowing aggregation of non-lease components with related lease components when evaluating accounting treatment for all classes of underlying assets. Adoption of the new standard resulted in an initial increase to assets and liabilities of $2,632 related to recognition of operating lease right-of-use assets and operating lease obligations as of September 2, 2019. Other line item impacts in the Company's condensed consolidated balance sheet were not material. The standard did not materially impact the condensed consolidated statements of income and cash flows. For more information on the Company's lease arrangements refer to Note 5.