Quarterly Financial Data (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended							4 Months Ended		12 Months Ended
	May 13, 2018	Feb. 18, 2018	Nov. 26, 2017	May 07, 2017		Feb. 12, 2017	Nov. 20, 2016	Sep. 02, 2018	Sep. 03, 2017	Sep. 02, 2018	Sep. 03, 2017	Aug. 28, 2016
REVENUE
Total revenue	$ 32,361	$ 32,995	$ 31,809	$ 28,860		$ 29,766	$ 28,099	$ 44,411	$ 42,300	$ 141,576	$ 129,025	$ 118,719
OPERATING EXPENSES
Merchandise costs	28,131	28,733	27,617	24,970		25,927	24,288	38,671	36,697	123,152	111,882	102,901
Selling, general and administrative	3,155	3,234	3,224	2,907		2,980	2,940	4,263	4,123	13,876	12,950	12,068
Preopening expenses	8	12	17	15		15	22	31	30	68	82	78
Operating Income	1,067	1,016	951	968		844	849	1,446	1,450	4,480	4,111	3,672
OTHER INCOME (EXPENSE)
Interest expense	(37)	(37)	(37)	(21)		(31)	(29)	(48)	(53)	(159)	(134)	(133)
Interest income and other, net	41	7	22	18		(4)	26	51	22	121	62	80
INCOME BEFORE INCOME TAXES	1,071	986	936	965		809	846	1,449	1,419	4,442	4,039	3,619
Provision for income taxes	309	273	285	259	[1]	288	291	396	487	1,263	1,325	1,243
Net income including noncontrolling interests	762	713	651	706		521	555	1,053	932	3,179	2,714	2,376
Net income attributable to noncontrolling interests	(12)	(12)	(11)	(6)		(6)	(10)	(10)	(13)	(45)	(35)	(26)
NET INCOME ATTRIBUTABLE TO COSTCO	$ 750	$ 701	$ 640	$ 700		$ 515	$ 545	$ 1,043	$ 919	$ 3,134	$ 2,679	$ 2,350
Dividends Payable [Line Items]
Basic	$ 1.71	$ 1.60	$ 1.46	$ 1.59		$ 1.17	$ 1.24	$ 2.38	$ 2.10	$ 7.15	$ 6.11	$ 5.36
Diluted	$ 1.70	$ 1.59	$ 1.45	$ 1.59		$ 1.17	$ 1.24	$ 2.36	$ 2.08	$ 7.09	$ 6.08	$ 5.33
Shares used in calculation (000's)
Basic (shares)	438,740	439,022	437,965	438,817		439,127	438,007	438,379	437,987	438,515	438,437	438,585
Diluted (shares)	441,715	441,568	440,851	441,056		440,657	440,525	442,427	441,036	441,834	440,937	441,263
CASH DIVIDEND DECLARED PER COMMON SHARE	$ 0.57	$ 0.5	$ 0.5	$ 7.5	[2]	$ 0.45	$ 0.45	$ 0.57	$ 0.5	$ 2.14	$ 8.90	$ 1.70
Net sales
REVENUE
Total revenue	$ 31,624	$ 32,279	$ 31,117	$ 28,216		$ 29,130	$ 27,469	$ 43,414	$ 41,357	$ 138,434	$ 126,172	$ 116,073
Membership fees
REVENUE
Total revenue	$ 737	$ 716	$ 692	$ 644		$ 636	$ 630	$ 997	$ 943	$ 3,142	2,853	$ 2,646
Special Dividend [Member]
Dividends Payable [Line Items]
Effective income tax rate reconciliation, deduction, dividends, amount											$ 82
Dividends paid per share											$ 7.00

[1] Includes an $82 tax benefit recorded in the third quarter in connection with the special cash dividend paid to employees through the Company's 401(k) Retirement Plan.

[2] Includes the special cash dividend of $7.00 per share paid in May 2017.