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 10, 2015	May 11, 2014	May 10, 2015	May 11, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			$ 12,515	$ 11,012
Comprehensive income:
Net income	519	479	1,631	1,383
Foreign-currency translation adjustment and other, net	76	90	(656)	54
COMPREHENSIVE INCOME ATTRIBUTABLE TO COSTCO	587	561	960	1,414
Comprehensive income	595	569	975	1,437
Comprehensive loss, net of tax, attributable to noncontrolling interest	8	8	15	23
Stock-based compensation			301	251
Stock options exercised, including tax effects			68	35
Release of vested restricted stock units (RSUs), including tax effects			(121)	(101)
Repurchases of common stock	(124)	(184)	(234)	(184)
Cash dividends declared			(2,690)	(429)
Equity at end of period	10,814	12,021	10,814	12,021
Attributable to Costco
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			12,303	10,833
Comprehensive income:
Net income			1,610	1,361
Foreign-currency translation adjustment and other, net			(650)	53
Stock-based compensation			301	251
Stock options exercised, including tax effects			68	35
Release of vested restricted stock units (RSUs), including tax effects			(121)	(101)
Repurchases of common stock			(234)	(184)
Cash dividends declared			(2,690)	(429)
Equity at end of period	10,587	11,819	10,587	11,819
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			212	179
Comprehensive income:
Net income			21	22
Foreign-currency translation adjustment and other, net			(6)	1
Equity at end of period	$ 227	$ 202	$ 227	$ 202