Note 11 - Common Stock and Earnings Per Share (Details) - Weighted Average Shares Outstanding (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014
Basic EPS
Income available to common stockholders (in Dollars)	$ 61,598	$ 52,426	$ 117,458	$ 104,604
Income available to common stockholders	41,630	42,547	41,658	42,840
Income available to common stockholders (in Dollars per share)	$ 1.48	$ 1.23	$ 2.82	$ 2.44
Diluted EPS
Dilutive effect of stock options and restricted stock	676	560	666	592
Income available to common stockholders plus assumed conversions (in Dollars)	$ 61,598	$ 52,426	$ 117,458	$ 104,604
Income available to common stockholders plus assumed conversions	42,306	43,107	42,324	43,432
Income available to common stockholders plus assumed conversions (in Dollars per share)	$ 1.46	$ 1.22	$ 2.78	$ 2.41