Stock-Based Compensation (Weighted Average Assumptions Using Black-Scholes Option Pricing) (Details)	12 Months Ended
	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2009
Dividend yield	1.25%	1.51%	2.01%
Non-Employee Directors' Stock Option Plan [Member]
Risk-free interest rate	2.13%	2.54%	1.45%
Expected life	5.43	5.43	5.51
Expected volatility	31.10%	35.40%	35.20%
Dividend yield	1.18%	1.42%	1.70%
Employee Stock Purchase Plan [Member]
Risk-free interest rate	0.10%	0.12%	0.31%
Expected life	3	3	3
Expected volatility	11.90%	13.80%	24.60%
Dividend yield	1.04%	1.33%	1.72%