Document And Entity Information	3 Months Ended
	Nov. 20, 2011	Dec. 09, 2011
Document And Entity Information [Abstract]
Document Type	10-Q
Document Period End Date	Nov. 20, 2011
Amendment Flag	false
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q1
Entity Registrant Name	COSTCO WHOLESALE CORP /NEW
Entity Central Index Key	0000909832
Current Fiscal Year End Date	--09-02
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		434,928,977