Summary of Significant Accounting Policies (Policies)	6 Months Ended
Feb. 18, 2024
Accounting Policies [Abstract]
Basis of Accounting, Policy	Basis of Presentation The condensed consolidated financial statements include the accounts of Costco and its wholly-owned subsidiaries. All material inter-company transactions among the Company and its consolidated subsidiaries have been eliminated in consolidation. 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 on Form 10-K for the fiscal year ended September 3, 2023.
Fiscal Period, Policy	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 2024 is a 52-week year ending on September 1, 2024. References to the second quarter of 2024 and 2023 relate to the 12-week fiscal quarters ended February 18, 2024, and February 12, 2023. References to the first half of 2024 and 2023 relate to the 24 weeks ended February 18, 2024 and February 12, 2023.
Use of Estimates, Policy	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. These estimates and assumptions take into account historical and forward-looking factors that the Company believes are reasonable. Actual results could differ from those estimates and assumptions.
Reclassification, Policy	Reclassification Reclassifications were made to the condensed consolidated statement of cash flows for the first half of fiscal 2023 to conform with current year presentation.
Recent Accounting Pronouncements Not Yet Adopted, Policy	Recent Accounting Pronouncements Not Yet Adopted In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2023-07, which is intended to improve reportable segment disclosure requirements, primarily through additional disclosures about significant segment expenses. The standard is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. The amendments should be applied retrospectively to all prior periods presented in the financial statements. The Company is evaluating the new standard. In December 2023, the FASB issued ASU 2023-09, which focuses on income tax disclosures by requiring public business entities, on an annual basis, to disclose specific categories in the rate reconciliation, provide information for reconciling items that meet a quantitative threshold, and certain information about income taxes paid. The standard is effective for annual periods beginning after December 15, 2024, with early adoption permitted. The amendments should be applied on a prospective basis. Retrospective application is permitted. The Company is evaluating the new standard.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Feb. 18, 2024

Basis of Presentation

The condensed consolidated financial statements include the accounts of Costco and its wholly-owned subsidiaries. All material inter-company transactions among the Company and its consolidated subsidiaries have been eliminated in consolidation.

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 on Form 10-K for the fiscal year ended September 3, 2023.

Fiscal Period, Policy

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 2024 is a 52-week year ending on September 1, 2024. References to the second quarter of 2024 and 2023 relate to the 12-week fiscal quarters ended February 18, 2024, and February 12, 2023. References to the first half of 2024 and 2023 relate to the 24 weeks ended February 18, 2024 and February 12, 2023.

Use of Estimates, Policy

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. These estimates and assumptions take into account historical and forward-looking factors that the Company believes are reasonable. Actual results could differ from those estimates and assumptions.

Reclassification, Policy

Reclassification

Reclassifications were made to the condensed consolidated statement of cash flows for the first half of fiscal 2023 to conform with current year presentation.

Recent Accounting Pronouncements Not Yet Adopted, Policy

Recent Accounting Pronouncements Not Yet Adopted

In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2023-07, which is intended to improve reportable segment disclosure requirements, primarily through additional disclosures about significant segment expenses. The standard is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. The amendments should be applied retrospectively to all prior periods presented in the financial statements. The Company is evaluating the new standard.

In December 2023, the FASB issued ASU 2023-09, which focuses on income tax disclosures by requiring public business entities, on an annual basis, to disclose specific categories in the rate reconciliation, provide information for reconciling items that meet a quantitative threshold, and certain information about income taxes paid. The standard is effective for annual periods beginning after December 15, 2024, with early adoption permitted. The amendments should be applied on a prospective basis. Retrospective application is permitted. The Company is evaluating the new standard.