Changes in Equity Attributes to Costco and the Noncontrolling Interests of Consolidated Subsidiaries (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 18, 2018	Feb. 12, 2017	Feb. 18, 2018	Feb. 12, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			$ (11,079)	$ (12,332)
Comprehensive income:
Net income	$ 713	$ 521	1,364	1,076
Foreign-currency translation adjustment and other, net	150	114	127	(231)
COMPREHENSIVE INCOME ATTRIBUTABLE TO COSTCO	841	621	1,458	826
Comprehensive income (loss), net of tax, attributable to noncontrolling interest	22	14	33	19
Comprehensive income	863	635	1,491	845
Stock-based compensation			348	322
Release of vested restricted stock units (RSUs), including tax effects			216	164
Repurchase of common stock	(59)	(66)	(178)	(188)
Cash dividends declared and other			(471)	(435)
Equity at end of period	(12,053)	(12,712)	(12,053)	(12,712)
Attributable to Costco
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			(10,778)	(12,079)
Comprehensive income:
Net income			1,341	1,060
Foreign-currency translation adjustment and other, net			117	(234)
COMPREHENSIVE INCOME ATTRIBUTABLE TO COSTCO			1,458	826
Stock-based compensation			348	322
Release of vested restricted stock units (RSUs), including tax effects			216	(164)
Repurchase of common stock			(178)	(188)
Cash dividends declared and other			(436)	(435)
Equity at end of period	(11,754)	12,440	(11,754)	12,440
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity at beginning of period			(301)	(253)
Comprehensive income:
Net income			23	16
Foreign-currency translation adjustment and other, net			10	3
Comprehensive income (loss), net of tax, attributable to noncontrolling interest			33	19
Cash dividends declared and other			(35)	0
Equity at end of period	$ (299)	$ (272)	$ (299)	$ (272)