EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2017	May 31, 2016
EARNINGS PER SHARE [Abstract]
Net income	$ 18,838	$ 16,837	$ 70,926	$ 66,451
Less: Allocation of income to unvested stockholders	(272)	(288)	(1,034)	(1,041)
Net earnings available to common stockholders	$ 18,566	$ 16,549	$ 69,892	$ 65,410
Basic weighted average shares outstanding	30,043	29,951	30,010	29,918
Add dilutive effect of stock options (two-class method)	2	4	4	5
Diluted average shares outstanding	30,045	29,955	30,014	29,923
Basic net income per share	$ 0.62	$ 0.55	$ 2.34	$ 2.19
Diluted net income per share	$ 0.62	$ 0.55	$ 2.34	$ 2.19