Document and Entity Information - USD ($)	12 Months Ended
	Aug. 28, 2016	Oct. 04, 2016	Feb. 14, 2016
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Aug. 28, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Trading Symbol	COST
Entity Registrant Name	COSTCO WHOLESALE CORP /NEW
Entity Central Index Key	0000909832
Current Fiscal Year End Date	--08-28
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		437,126,569
Entity Public Float			$ 64,810,523,114