Note 12 - Weighted Average Shares Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2016	May 31, 2015
Income available to common stockholders, net income (numerator)	$ 66,781	$ 61,409	$ 194,508	$ 178,867
Income available to common stockholders, weighted average common share (denominator) (in shares)	40,779	41,628	41,094	41,648
Income available to common stockholders, per share amount (in dollars per share)	$ 1.64	$ 1.48	$ 4.73	$ 4.29
Dilutive effect of stock options and restricted stock, weighted average common share (denominator) (in shares)	410	669	502	669
Income available to common stockholders plus assumed conversions, net income (numerator)	$ 66,781	$ 61,409	$ 194,508	$ 178,867
Income available to common stockholders plus assumed conversions, weighted average common share (denominator) (in shares)	41,189	42,297	41,596	42,317
Income available to common stockholders plus assumed conversions, per share amount (in dollars per share)	$ 1.62	$ 1.45	$ 4.68	$ 4.23