Changes in Equity Attributes to Costco and the Noncontrolling Interests of Consolidated Subsidiaries (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 12, 2017	Feb. 14, 2016	Feb. 12, 2017	Feb. 14, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			$ 12,332	$ 10,843
Comprehensive income:
Net income	$ 521	$ 555	1,076	1,042
Foreign-currency translation adjustment and other, net	114	(244)	(231)	(229)
COMPREHENSIVE INCOME ATTRIBUTABLE TO COSTCO	621	307	826	803
Comprehensive income (loss), net of tax, attributable to noncontrolling interest	14	4	19	10
Comprehensive income	635	311	845	813
Stock-based compensation			322	287
Release of vested restricted stock units (RSUs), including tax effects			(164)	(145)
Repurchases of common stock	(66)	(80)	(188)	(210)
Cash dividends declared			(435)	(352)
Distribution to noncontrolling interest				(2)
Equity at end of period	12,712	11,234	12,712	11,234
Attributable to Costco
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			12,079	10,617
Comprehensive income:
Net income			1,060	1,026
Foreign-currency translation adjustment and other, net			(234)	(223)
COMPREHENSIVE INCOME ATTRIBUTABLE TO COSTCO			826	803
Stock-based compensation			322	287
Release of vested restricted stock units (RSUs), including tax effects			(164)	(145)
Repurchases of common stock			(188)	(210)
Cash dividends declared			(435)	(352)
Equity at end of period	12,440	11,000	12,440	11,000
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			253	226
Comprehensive income:
Net income			16	16
Foreign-currency translation adjustment and other, net			3	(6)
Comprehensive income (loss), net of tax, attributable to noncontrolling interest			19	10
Distribution to noncontrolling interest				(2)
Equity at end of period	$ 272	$ 234	$ 272	$ 234