Quarterly Financial Data (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended							4 Months Ended		12 Months Ended
	May 11, 2014	Feb. 16, 2014	Nov. 24, 2013	May 12, 2013	Feb. 17, 2013		Nov. 25, 2012	Aug. 31, 2014	Sep. 01, 2013	Aug. 31, 2014	Sep. 01, 2013	Sep. 02, 2012	Nov. 28, 2012
Quarterly Financial Information Disclosure [Abstract]
Nonrecurring Tax Expense Benefit											$ 62
Special Cash Dividend Declared And Paid Per Share													$ 7.00
REVENUE
Net sales	25,233	25,756	24,468	23,552	24,343		23,204	34,755	31,771	110,212	102,870	97,062
Membership fees	561	550	549	531	528		511	768	716	2,428	2,286	2,075
Total revenue	25,794	26,306	25,017	24,083	24,871		23,715	35,523	32,487	112,640	105,156	99,137
OPERATING EXPENSES
Merchandise costs	22,554	23,043	21,824	21,038	21,766		20,726	31,037	28,418	98,458	91,948	86,823
Selling, general and administrative	2,487	2,531	2,501	2,313	2,361		2,332	3,380	3,098	10,899	10,104	9,518
Preopening expenses	16	8	24	10	6		18	15	17	63	51	37
Operating income	737	724	668	722	738		639	1,091	954	3,220	3,053	2,759
OTHER INCOME (EXPENSE)
Interest expense	(25)	(26)	(27)	(25)	(25)		(13)	(35)	(36)	(113)	(99)	(95)
Interest income and other, net	12	30	18	15	26		20	30	36	90	97	103
INCOME BEFORE INCOME TAXES	724	728	659	712	739		646	1,086	954	3,197	3,051	2,767
Provision for income taxes	245	255	228	248	185	[1]	225	381	332	1,109	990	1,000
Net income including noncontrolling interests	479	473	431	464	554		421	705	622	2,088	2,061	1,767
Net income attributable to noncontrolling interests	(6)	(10)	(6)	(5)	(7)		(5)	(8)	(5)	(30)	(22)	(58)
NET INCOME ATTRIBUTABLE TO COSTCO	$ 473	$ 463	$ 425	$ 459	$ 547		$ 416	$ 697	$ 617	$ 2,058	$ 2,039	$ 1,709
NET INCOME PER COMMON SHARE ATTRIBUTABLE TO COSTCO:
Basic	$ 1.08	$ 1.05	$ 0.97	$ 1.05	$ 1.26		$ 0.96	$ 1.59	$ 1.41	$ 4.69	$ 4.68	$ 3.94
Diluted	$ 1.07	$ 1.05	$ 0.96	$ 1.04	$ 1.24		$ 0.95	$ 1.58	$ 1.40	$ 4.65	$ 4.63	$ 3.89
Shares used in calculation (000's)
Basic (shares)	439,446	439,776	437,970	436,488	435,975		433,423	437,875	436,752	438,693	435,741	433,620
Diluted (shares)	442,720	442,829	442,420	440,780	439,812		438,643	441,887	441,907	442,485	440,512	439,373
Common Stock, Dividends, Per Share, Declared	$ 0.355	$ 0.31	$ 0.31	$ 0.31	$ 7.275	[2]	$ 0.275	$ 0.355	$ 0.31	$ 1.33	$ 8.17	$ 1.03

[1] Includes a $62 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 $7.00 per share paid in December 2012.