Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended							4 Months Ended		12 Months Ended
	May. 10, 2015	Feb. 15, 2015		Nov. 23, 2014	May. 11, 2014	Feb. 16, 2014	Nov. 24, 2013	Aug. 30, 2015	Aug. 31, 2014	Aug. 30, 2015	Aug. 31, 2014	Sep. 01, 2013
REVENUE
Net sales	$ 25,517	$ 26,872		$ 26,284	$ 25,233	$ 25,756	$ 24,468	$ 34,993	$ 34,755	$ 113,666	$ 110,212	$ 102,870
Membership fees	584	582		582	561	550	549	785	768	2,533	2,428	2,286
Total revenue	26,101	27,454		26,866	25,794	26,306	25,017	35,778	35,523	116,199	112,640	105,156
OPERATING EXPENSES
Merchandise costs	22,687	23,897		23,385	22,554	23,043	21,824	31,096	31,037	101,065	98,458	91,948
Selling, general and administrative	2,579	2,671		2,696	2,487	2,531	2,501	3,499	3,380	11,445	10,899	10,104
Preopening expenses	14	9		15	16	8	24	27	15	65	63	51
Operating income	821	877		770	737	724	668	1,156	1,091	3,624	3,220	3,053
OTHER INCOME (EXPENSE)
Interest expense	(31)	(27)		(26)	(25)	(26)	(27)	(40)	(35)	(124)	(113)	(99)
Interest income and other, net	9	20		35	12	30	18	40	30	104	90	97
INCOME BEFORE INCOME TAXES	799	870		779	724	728	659	1,156	1,086	3,604	3,197	3,051
Provision for income taxes	280	263	[1]	274	245	255	228	378	381	1,195	1,109	990
Net income including noncontrolling interests	519	607		505	479	473	431	778	705	2,409	2,088	2,061
Net income attributable to noncontrolling interests	(3)	(9)		(9)	(6)	(10)	(6)	(11)	(8)	(32)	(30)	(22)
NET INCOME ATTRIBUTABLE TO COSTCO	$ 516	$ 598		$ 496	$ 473	$ 463	$ 425	$ 767	$ 697	$ 2,377	$ 2,058	$ 2,039
NET INCOME PER COMMON SHARE ATTRIBUTABLE TO COSTCO:
Basic	$ 1.17	$ 1.36		$ 1.13	$ 1.08	$ 1.05	$ 0.97	$ 1.75	$ 1.59	$ 5.41	$ 4.69	$ 4.68
Diluted	$ 1.17	$ 1.35		$ 1.12	$ 1.07	$ 1.05	$ 0.96	$ 1.73	$ 1.58	$ 5.37	$ 4.65	$ 4.63
Shares used in calculation (000's)
Basic (shares)	440,070	440,384		438,760	439,446	439,776	437,970	438,835	437,875	439,455	438,693	435,741
Diluted (shares)	443,132	442,896		442,210	442,720	442,829	442,420	442,404	441,887	442,716	442,485	440,512
CASH DIVIDENDS DECLARED PER COMMON SHARE	$ 0.40	$ 5.355	[2]	$ 0.355	$ 0.355	$ 0.31	$ 0.31	$ 0.40	$ 0.355	$ 6.51	$ 1.33	$ 8.17
Special Dividend [Member]
Quarterly Financial Data [Line Items]
Effective income tax rate reconciliation, deduction, dividends, amount										$ 57		$ 62
Dividends paid per share										$ 5		$ 7

[1] Includes a $57 tax benefit recorded in the second 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 $5.00 per share paid in February 2015.