CONSOLIDATED STATEMENTS OF INCOME (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2014	May 31, 2013
Revenues:
Net warehouse club sales	$ 597,885	$ 555,815	$ 1,844,746	$ 1,671,269
Export sales	6,577	6,224	19,062	15,620
Membership income	9,552	8,774	28,301	24,773
Other income	1,023	909	2,903	2,756
Total revenues	615,037	571,722	1,895,012	1,714,418
Cost of goods sold:
Net warehouse club	509,684	475,727	1,575,623	1,425,396
Export	6,246	5,907	18,110	14,728
Selling, general and administrative:
Warehouse club operations	53,617	49,421	158,592	143,476
General and administrative	12,604	11,404	37,065	34,450
Pre-opening expenses	1,125	525	1,939	1,409
Loss/(gain) on disposal of assets	558	249	746	353
Total operating expenses	583,834	543,233	1,792,075	1,619,812
Operating income	31,203	28,489	102,937	94,606
Other income (expense):
Interest income	202	338	576	1,078
Interest expense	(1,043)	(427)	(2,967)	(2,951)
Other income (expense), net	489	(785)	1,512	(1,051)
Total other expense	(352)	(874)	(879)	(2,924)
Income from continuing operations before provision for income taxes and loss of unconsolidated affiliates	30,851	27,615	102,058	91,682
Provision for income taxes	(9,534)	(9,082)	(31,035)	(28,254)
Income (loss) of unconsolidated affiliates	3	6	7	(2)
Net income	$ 21,320	$ 18,539	$ 71,030	$ 63,426
Net income per share available for distribution:
Basic net income per share from continuing operations (in dollars per share)	$ 0.70	$ 0.61	$ 2.35	$ 2.09
Basic net income per share (in dollars per share)	$ 0.70	$ 0.61	$ 2.35	$ 2.09
Diluted net income per share from continuing operations (in dollars per share)	$ 0.70	$ 0.61	$ 2.34	$ 2.09
Diluted net income per share (in dollars per share)	$ 0.70	$ 0.61	$ 2.34	$ 2.09
Shares used in per share computations:
Basic (in shares)	29,784	29,683	29,733	29,634
Diluted (in shares)	29,792	29,692	29,743	29,644
Dividends per share (in dollars per share)	$ 0.00	$ 0.00	$ 0.70	$ 0.60
Statement [Line Items]
Document Fiscal Year Focus			2014