QUARTERLY FINANCIAL INFORMATION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Total net warehouse club and export sales	$ 719,874	$ 717,174	$ 780,445	$ 726,813	$ 698,316	$ 691,638	$ 765,536	$ 699,063	$ 686,436	$ 684,780	$ 738,349	$ 644,846	$ 2,944,306	$ 2,854,553	$ 2,754,411
Total cost of goods sold	615,920	617,598	667,563	618,671	596,644	597,242	657,725	598,015	586,114	587,860	631,810	547,055	2,519,752	2,449,626	2,352,839
Net income	$ 19,798	$ 18,838	$ 27,219	$ 24,869	$ 22,272	$ 16,837	$ 25,942	$ 23,672	$ 22,447	$ 21,195	$ 24,835	$ 20,647	$ 90,724	$ 88,723	$ 89,124
Basic net income per share	$ 0.64	$ 0.62	$ 0.90	$ 0.82	$ 0.74	$ 0.55	$ 0.85	$ 0.78	$ 0.75	$ 0.70	$ 0.82	$ 0.68	$ 2.98	$ 2.92	$ 2.95
Diluted net income per share	$ 0.64	$ 0.62	$ 0.90	$ 0.82	$ 0.74	$ 0.55	$ 0.85	$ 0.78	$ 0.75	$ 0.70	$ 0.82	$ 0.68	$ 2.98	$ 2.92	$ 2.95