Consolidated Statements Of Income - 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
REVENUE
Total revenue	$ 34,740	$ 35,396	$ 35,069	$ 32,361	$ 32,995	$ 31,809	$ 47,498	$ 44,411	$ 152,703	$ 141,576	$ 129,025
OPERATING EXPENSES
Merchandise costs	30,233	30,720	30,623	28,131	28,733	27,617	41,310	38,671	132,886	123,152	111,882
Selling, general and administrative	3,371	3,464	3,475	3,155	3,234	3,224	4,684	4,263	14,994	13,876	12,950
Preopening expenses	14	9	22	8	12	17	41	31	86	68	82
Operating Income	1,122	1,203	949	1,067	1,016	951	1,463	1,446	4,737	4,480	4,111
OTHER INCOME (EXPENSE)
Interest expense	(35)	(34)	(36)	(37)	(37)	(37)	(45)	(48)	(150)	(159)	(134)
Interest income and other, net	36	46	22	41	7	22	74	51	178	121	62
INCOME BEFORE INCOME TAXES	1,123	1,215	935	1,071	986	936	1,492	1,449	4,765	4,442	4,039
Provision for income taxes	207	314	158	309	273	285	382	396	1,061	1,263	1,325
Net income including noncontrolling interests	916	901	777	762	713	651	1,110	1,053	3,704	3,179	2,714
Net income attributable to noncontrolling interests	(10)	(12)	(10)	(12)	(12)	(11)	(13)	(10)	(45)	(45)	(35)
NET INCOME ATTRIBUTABLE TO COSTCO	$ 906	$ 889	$ 767	$ 750	$ 701	$ 640	$ 1,097	$ 1,043	$ 3,659	$ 3,134	$ 2,679
NET INCOME PER COMMON SHARE ATTRIBUTABLE TO COSTCO:
Basic (in dollars per share)	$ 2.06	$ 2.02	$ 1.75	$ 1.71	$ 1.60	$ 1.46	$ 2.49	$ 2.38	$ 8.32	$ 7.15	$ 6.11
Diluted (in dollars per share)	$ 2.05	$ 2.01	$ 1.73	$ 1.70	$ 1.59	$ 1.45	$ 2.47	$ 2.36	$ 8.26	$ 7.09	$ 6.08
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Basic (shares)	439,859	440,284	439,157	438,740	439,022	437,965	439,727	438,379	439,755	438,515	438,437
Diluted (shares)	442,642	442,337	442,749	441,715	441,568	440,851	443,400	442,427	442,923	441,834	440,937
Net sales
REVENUE
Total revenue	$ 33,964	$ 34,628	$ 34,311	$ 31,624	$ 32,279	$ 31,117	$ 46,448	$ 43,414	$ 149,351	$ 138,434	$ 126,172
Membership fees
REVENUE
Total revenue	$ 776	$ 768	$ 758	$ 737	$ 716	$ 692	$ 1,050	$ 997	$ 3,352	$ 3,142	$ 2,853