Document and Entity Information	9 Months Ended
	May 11, 2014	May 28, 2014
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	May 11, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q3
Trading Symbol	COST
Entity Registrant Name	COSTCO WHOLESALE CORP /NEW
Entity Central Index Key	0000909832
Current Fiscal Year End Date	--08-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		438,295,696