Share-Based Compensation (Details 2) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Nov. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted	0
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized shared-based compensation cost	$ 65.6
Performance share awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized shared-based compensation cost	2.8
Restricted stock units and performance share awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted	65,000
Weighted average fair value of granted awards	$ 26.63
Weighted average period unrecognized share-based compensation expected to be recognized	2 years 8 months 12 days
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized shared-based compensation cost	$ 7.7
Weighted average period unrecognized share-based compensation expected to be recognized	1 year 10 months 24 days