Condensed Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Feb. 12, 2012	Feb. 13, 2011
CASH FLOWS FROM OPERATING ACTIVITIES
Net income including noncontrolling interests	$ 740	$ 701
Adjustments to reconcile net income including noncontrolling interests to net cash provided by operating activities:
Depreciation and amortization	414	386
Stock-based compensation	134	109
Excess tax benefits on stock-based awards	(40)	(28)
Other non-cash operating activities, net	19	9
Deferred income taxes	(7)	(6)
Changes in operating assets and liabilities:
Increase in merchandise inventories	(327)	(151)
(Decrease)/increase in accounts payable	(75)	100
Other operating assets and liabilities, net	386	326
Net cash provided by operating activities	1,244	1,446
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of short-term investments	(869)	(1,884)
Maturities of short-term investments	867	981
Sales of investments	191	414
Additions to property and equipment	(632)	(540)
Proceeds from the sale of property and equipment	8	8
Increase resulting from initial consolidation of Costco Mexico	0	165
Other investing activities, net	(17)	(5)
Net cash used in investing activities	(452)	(861)
CASH FLOWS FROM FINANCING ACTIVITIES
Change in bank checks outstanding	(77)	(319)
Repayments of short-term borrowings	(117)	(33)
Proceeds from short-term borrowings	117	8
Proceeds from issuance of long-term debt	129	0
Proceeds from exercise of stock options	39	193
Minimum tax withholdings on stock-based awards	(104)	(52)
Excess tax benefits on stock-based awards	40	28
Repurchases of common stock	(312)	(239)
Cash dividend payments	(105)	(89)
Other financing activities, net	(2)	0
Net cash used in financing activities	(392)	(503)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	(20)	59
Net increase in cash and cash equivalents	380	141
CASH AND CASH EQUIVALENTS BEGINNING OF YEAR	4,009	3,214
CASH AND CASH EQUIVALENTS END OF PERIOD	4,389	3,355
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Interest (reduced by $4 and $4 interest capitalized in 2012 and 2011, respectively)	56	55
Income taxes	363	257
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Decrease in accrued property and equipment	66	50
Cash dividend declared, but not yet paid	104	90
Unsettled repurchases of common stock	$ 6	$ 6