Note 12 - Common Stock and Earnings Per Share - Weighted Average Shares Outstanding (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
Income available to common stockholders plus assumed conversions, net income (numerator)	$ 65,414	$ 66,781	$ 198,707	$ 194,508
Diluted weighted average common shares (in shares)	39,457	41,189	39,736	41,596
Diluted earnings per common share (in dollars per share)	$ 1.66	$ 1.62	$ 5	$ 4.68
Income available to common stockholders, net income (numerator)	$ 65,414	$ 66,781	$ 198,707	$ 194,508
Basic weighted average common shares (in shares)	39,317	40,779	39,528	41,094
Basic earnings per common share (in dollars per share)	$ 1.66	$ 1.64	$ 5.03	$ 4.73
Dilutive effect of stock options and restricted stock, weighted average common share (denominator) (in shares)	140	410	208	502