Changes in Equity Attributes to Costco and the Noncontrolling Interests of Consolidated Subsidiaries (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	May 11, 2014	May 12, 2013	May 11, 2014	May 12, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			$ 11,012	$ 12,518
Comprehensive income:
Net income	479	464	1,383	1,439
Net Income (Loss) Attributable to Parent	473	459	1,361	1,422
Net Income (Loss) Attributable to Noncontrolling Interest	6	5	22	17
Foreign-currency translation adjustment and other, net	90	(31)	54	(74)
COMPREHENSIVE INCOME ATTRIBUTABLE TO COSTCO	561	429	1,414	1,347
Comprehensive income	569	433	1,437	1,365
Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest	8	4	23	18
Stock-based compensation			251	210
Stock options exercised, including tax effects			35	67
Release of vested restricted stock units (RSUs), including tax effects			(101)	(85)
Conversion of convertible notes				30
Repurchases of common stock	(184)	0	(184)	(34)
Cash dividends declared			(429)	(3,424)
Equity at end of period	12,021	10,647	12,021	10,647
Attributable to Costco
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			10,833	12,361
Comprehensive income:
Net Income (Loss) Attributable to Parent			1,361	1,422
Foreign-currency translation adjustment and other, net			53	(75)
Stock-based compensation			251	210
Stock options exercised, including tax effects			35	67
Release of vested restricted stock units (RSUs), including tax effects			(101)	(85)
Conversion of convertible notes				30
Repurchases of common stock			(184)	(34)
Cash dividends declared			(429)	(3,424)
Equity at end of period	11,819	10,472	11,819	10,472
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			179	157
Comprehensive income:
Net Income (Loss) Attributable to Noncontrolling Interest			22	17
Foreign-currency translation adjustment and other, net			1	1
Equity at end of period	$ 202	$ 175	$ 202	$ 175