Stock and Savings Plans (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Aug. 31, 2011 Years	Aug. 31, 2010	Aug. 31, 2009
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized shared-based compensation cost	$ 34.4
Weighted average period unrecognized share-based compensation expected to be recognized	2.08
Fair value of share-based awards vested	37.8	45.4	54.1
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized shared-based compensation cost	105.5
Fair value of share-based awards vested	25.5	24.8	23.2
Performance share awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized shared-based compensation cost	$ 10.9
Restricted stock units and performance share awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period unrecognized share-based compensation expected to be recognized	2.52