Note 11. Common Stock and Earnings Per Share (Detail) - Weighted Average Shares Outstanding (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Income available to common stockholders (in Dollars)	$ 188,809	$ 171,046	$ 150,211
Income available to common stockholders	44,784	45,953	46,698
Income available to common stockholders (in Dollars per share)	$ 4.22	$ 3.72	$ 3.22
Dilutive effect of stock options and restricted stock	1,026	1,402	1,306
Income available to common stockholders plus assumed conversions (in Dollars)	$ 188,809	$ 171,046	$ 150,211
Income available to common stockholders plus assumed conversions	45,810	47,355	48,004
Income available to common stockholders plus assumed conversions (in Dollars per share)	$ 4.12	$ 3.61	$ 3.13