Share-Based Compensation (Details 2) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended
	Nov. 30, 2012
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized shared-based compensation cost	$ 11.8
Weighted average period unrecognized share-based compensation expected to be recognized	1 year 11 months 16 days
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized shared-based compensation cost	82.5
Performance share awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized shared-based compensation cost	$ 5.8
Restricted stock units and performance share awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted	76
Weighted average fair value of granted awards	$ 21.05
Weighted average period unrecognized share-based compensation expected to be recognized	2 years 3 months 18 days