Commitments and Contingencies	3 Months Ended
Nov. 25, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 9—Commitments and Contingencies Legal Proceedings The Company is involved in a number of claims, proceedings and litigation arising from its business and property ownership. In accordance with applicable accounting guidance, the Company establishes an accrual for legal proceedings if and when those matters reach a stage where they present loss contingencies that are both probable and reasonably estimable. There may be exposure to loss in excess of any amounts accrued. The Company monitors those matters for developments that would affect the likelihood of a loss (taking into account where applicable indemnification arrangements concerning suppliers and insurers) and the accrued amount, if any, thereof, and adjusts the amount as appropriate. As of the date of this Report, the Company has recorded an immaterial accrual with respect to one matter described below, in addition to other immaterial accruals for matters not described below. If the loss contingency at issue is not both probable and reasonably estimable, the Company does not establish an accrual, but will continue to monitor the matter for developments that will make the loss contingency both probable and reasonably estimable. In each case, there is a reasonable possibility that a loss may be incurred, including a loss in excess of the applicable accrual. For matters where no accrual has been recorded, the possible loss or range of loss (including any loss in excess of the accrual) cannot, in the Company's view, be reasonably estimated because, among other things: (i) the remedies or penalties sought are indeterminate or unspecified; (ii) the legal and/or factual theories are not well developed; and/or (iii) the matters involve complex or novel legal theories or a large number of parties. The Company is a defendant in a class action alleging violation of California Wage Order 7-2001 for failing to provide seating to member service assistants who act as greeters and exit attendants in the Company’s California warehouses. Canela v. Costco Wholesale Corp., et al. (Case No. 5:13-cv-03598, N.D. Cal. filed July 1, 2013). The complaint seeks relief under the California Labor Code, including civil penalties and attorneys’ fees. The Company filed an answer denying the material allegations of the complaint. The plaintiff has since indicated that exit attendants are no longer a subject of the litigation. The action in the district court has been stayed pending review by the Ninth Circuit of the order certifying a class. On September 6, 2018, counsel claiming to represent an employee notified the California Labor and Workforce Development agency of an intention to bring similar claims concerning Costco employees engaged at member services counters. On November 23, 2016, the Company’s Canadian subsidiary received from the Ontario Ministry of Health and Long Term Care a request for an inspection and information concerning compliance with the anti-rebate provisions in the Ontario Drug Benefit Act and the Drug Interchangeability and Dispensing Fee Act. The Ministry has indicated that it has reason to believe the Company received payments in violation of these laws and is seeking disgorgement of these sums, and the Company is engaged in discussions concerning a settlement payment. In December 2017, the United States Judicial Panel on Multidistrict Litigation consolidated numerous cases filed against various defendants by counties, cities, hospitals, Native American tribes and third-party payors concerning the impacts of opioid abuse. In re National Prescription Opiate Litigation (MDL No. 2804) (N.D. Ohio). Included are federal court cases that name the Company, including actions filed by a number of counties and cities in Michigan, New Jersey and Ohio, and a third-party payor in Ohio. Similar cases that name the Company are pending in state court in Oklahoma. The Company is defending all of these matters. The Company and its CEO and CFO are defendants in putative class actions brought on behalf of shareholders who acquired Company stock between June 6 and October 25, 2018. Johnson v. Costco Wholesale Corp., et al. (W.D. Wash. filed Nov. 5, 2018); Chen v. Costco Wholesale Corp., et al. (W.D. Wash. filed Dec. 11, 2018). The complaints allege violations of the federal securities laws stemming from the Company’s disclosures concerning internal control over financial reporting. They seek unspecified damages, equitable relief, interest, and costs and attorneys’ fees. The Company expects these actions to be vigorously defended. Members of the Board of Directors, one other individual, and the Company are defendants in a shareholder derivative action related to the internal controls and related disclosures identified in the putative class actions, alleging that the individual defendants breached their fiduciary duties. Wedekind v. Hamilton James, Susan Decker, Kenneth Denman, Richard Galanti, Craig Jelinek, Richard Libenson, John Meisenbach, Charles Munger, Jeffrey Raikes, John Stanton, Mary Agnes Wilderotter, and Costco Wholesale Corp. (W.D. Wash. filed Dec. 11, 2018). The complaint seeks unspecified damages, disgorgement of compensation, corporate governance changes, and costs and attorneys' fees. Because the complaint is derivative in nature, it does not seek monetary damages from the Company, which is a nominal defendant. In November 2016 and September 2017, the Company received notices of violation from the Connecticut Department of Energy and Environmental Protection regarding hazardous waste practices at its Connecticut warehouses, primarily concerning unsalable pharmaceuticals. The Company is seeking to cooperate concerning the resolution of these notices. The Company does not believe that any pending claim, proceeding or litigation, either alone or in the aggregate, will have a material adverse effect on the Company’s financial position, results of operations or cash flows; however, it is possible that an unfavorable outcome of some or all of the matters, however unlikely, could result in a charge that might be material to the results of an individual fiscal quarter.

Note 9—Commitments and Contingencies

Legal Proceedings

The Company is involved in a number of claims, proceedings and litigation arising from its business and property ownership. In accordance with applicable accounting guidance, the Company establishes an accrual for legal proceedings if and when those matters reach a stage where they present loss contingencies that are both probable and reasonably estimable. There may be exposure to loss in excess of any amounts accrued. The Company monitors those matters for developments that would affect the likelihood of a loss (taking into account where applicable indemnification arrangements concerning suppliers and insurers) and the accrued amount, if any, thereof, and adjusts the amount as appropriate. As of the date of this Report, the Company has recorded an immaterial accrual with respect to one matter described below, in addition to other immaterial accruals for matters not described below. If the loss contingency at issue is not both probable and reasonably estimable, the Company does not establish an accrual, but will continue to monitor the matter for developments that will make the loss contingency both probable and reasonably estimable. In each case, there is a reasonable possibility that a loss may be incurred, including a loss in excess of the applicable accrual. For matters where no accrual has been recorded, the possible loss or range of loss (including any loss in excess of the accrual) cannot, in the Company's view, be reasonably estimated because, among other things: (i) the remedies or penalties sought are indeterminate or unspecified; (ii) the legal and/or factual theories are not well developed; and/or (iii) the matters involve complex or novel legal theories or a large number of parties.

The Company is a defendant in a class action alleging violation of California Wage Order 7-2001 for failing to provide seating to member service assistants who act as greeters and exit attendants in the Company’s California warehouses. Canela v. Costco Wholesale Corp., et al. (Case No. 5:13-cv-03598, N.D. Cal. filed July 1, 2013). The complaint seeks relief under the California Labor Code, including civil penalties and attorneys’ fees. The Company filed an answer denying the material allegations of the complaint. The plaintiff has since indicated that exit attendants are no longer a subject of the litigation. The action in the district court has been stayed pending review by the Ninth Circuit of the order certifying a class. On September 6, 2018, counsel claiming to represent an employee notified the California Labor and Workforce Development agency of an intention to bring similar claims concerning Costco employees engaged at member services counters.

On November 23, 2016, the Company’s Canadian subsidiary received from the Ontario Ministry of Health and Long Term Care a request for an inspection and information concerning compliance with the anti-rebate provisions in the Ontario Drug Benefit Act and the Drug Interchangeability and Dispensing Fee Act. The Ministry has indicated that it has reason to believe the Company received payments in violation of these laws and is seeking disgorgement of these sums, and the Company is engaged in discussions concerning a settlement payment.

In December 2017, the United States Judicial Panel on Multidistrict Litigation consolidated numerous cases filed against various defendants by counties, cities, hospitals, Native American tribes and third-party payors concerning the impacts of opioid abuse. In re National Prescription Opiate Litigation (MDL No. 2804) (N.D. Ohio). Included are federal court cases that name the Company, including actions filed by a number of counties and cities in Michigan, New Jersey and Ohio, and a third-party payor in Ohio. Similar cases that name the Company are pending in state court in Oklahoma. The Company is defending all of these matters.

The Company and its CEO and CFO are defendants in putative class actions brought on behalf of shareholders who acquired Company stock between June 6 and October 25, 2018. Johnson v. Costco Wholesale Corp., et al. (W.D. Wash. filed Nov. 5, 2018); Chen v. Costco Wholesale Corp., et al. (W.D. Wash. filed Dec. 11, 2018). The complaints allege violations of the federal securities laws stemming from the Company’s disclosures concerning internal control over financial reporting. They seek unspecified damages, equitable relief, interest, and costs and attorneys’ fees. The Company expects these actions to be vigorously defended.

Members of the Board of Directors, one other individual, and the Company are defendants in a shareholder derivative action related to the internal controls and related disclosures identified in the putative class actions, alleging that the individual defendants breached their fiduciary duties. Wedekind v. Hamilton James, Susan Decker, Kenneth Denman, Richard Galanti, Craig Jelinek, Richard Libenson, John Meisenbach, Charles Munger, Jeffrey Raikes, John Stanton, Mary Agnes Wilderotter, and Costco Wholesale Corp. (W.D. Wash. filed Dec. 11, 2018). The complaint seeks unspecified damages, disgorgement of compensation, corporate governance changes, and costs and attorneys' fees. Because the complaint is derivative in nature, it does not seek monetary damages from the Company, which is a nominal defendant.

In November 2016 and September 2017, the Company received notices of violation from the Connecticut Department of Energy and Environmental Protection regarding hazardous waste practices at its Connecticut warehouses, primarily concerning unsalable pharmaceuticals. The Company is seeking to cooperate concerning the resolution of these notices.

The Company does not believe that any pending claim, proceeding or litigation, either alone or in the aggregate, will have a material adverse effect on the Company’s financial position, results of operations or cash flows; however, it is possible that an unfavorable outcome of some or all of the matters, however unlikely, could result in a charge that might be material to the results of an individual fiscal quarter.