Net Income per Common and Common Equivalent Share - Schedule of Earnings per Share Effect on Net Income and Weighted Averegae Number of Dilutive Potential Common Stock (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended						4 Months Ended		12 Months Ended
	May 12, 2019	Feb. 17, 2019	Nov. 25, 2018	May 13, 2018	Feb. 18, 2018	Nov. 26, 2017	Sep. 01, 2019	Sep. 02, 2018	Sep. 01, 2019	Sep. 02, 2018	Sep. 03, 2017
Earnings Per Share [Abstract]
NET INCOME ATTRIBUTABLE TO COSTCO	$ 906	$ 889	$ 767	$ 750	$ 701	$ 640	$ 1,097	$ 1,043	$ 3,659	$ 3,134	$ 2,679
Weighted average number of common shares used in basic net income per common share	439,859	440,284	439,157	438,740	439,022	437,965	439,727	438,379	439,755	438,515	438,437
RSUs and other									3,168	3,319	2,500
Weighted average number of common shares and dilutive potential of common stock used in diluted net income per share	442,642	442,337	442,749	441,715	441,568	440,851	443,400	442,427	442,923	441,834	440,937