Share-Based Compensation (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 29, 2012	Feb. 28, 2011	Feb. 29, 2012 years	Feb. 28, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Expense	$ 2.1	$ 3.9	$ 6.0	$ 6.0
Unrecognized pre-tax compensation cost, total	30.8		30.8
Period of unrecognized pre-tax compensation to be recognized			3
Share-based compensation, granted			$ 24.0
PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			three