Cover - shares	6 Months Ended
	Feb. 14, 2021	Mar. 03, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Feb. 14, 2021
Document Fiscal Year Focus	2021
Document Transition Report	false
Entity File Number	0-20355
Entity Registrant Name	COSTCO WHOLESALE CORP /NEW
Entity Incorporation, State or Country Code	WA
Entity Tax Identification Number	91-1223280
Entity Address, Address Line One	999 Lake Drive
Entity Address, City or Town	Issaquah
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	98027
City Area Code	425
Local Phone Number	313-8100
Title of 12(b) Security	Common Stock, $.01 Par Value
Trading Symbol	COST
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		442,533,785
Amendment Flag	false
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000909832
Current Fiscal Year End Date	--08-29