Consolidated Statements of Stockholders' Equity Parenthetical (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Cash dividends per common share	$ 0.72	$ 0.62	$ 0.60
Number of treasury stock shares acquired	1,463,000	1,011,000
Net Change in Net Actuarial Losses [Member]
Net change in net actuarial losses	$ 4,204	$ 4,178	$ 4,720
Net Change in Prior Service Costs (Credit) [Member]
Net change in net actuarial losses	$ 0	$ 0	$ 0