Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Nov. 30, 2011	Nov. 30, 2010	Aug. 31, 2011
Income Taxes [Abstract]
Effective income tax rate	23.10%	20.60%
Gross liability for unrecognized tax benefits, excluding interest and penalties	$ 27.2		$ 26.2
Liabilities for the payment of interest and penalties related to its unrecognized tax benefits	$ 5.3		$ 5.1

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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This element represents the total of accruals as of the date of the statement of financial position for interest recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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