Quarterly report pursuant to Section 13 or 15(d)

Income Taxes - Additional Information (Detail)

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Income Taxes - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Nov. 30, 2012
Nov. 30, 2011
Aug. 31, 2012
Income Taxes [Line Items]      
Effective income tax rate 18.50% 23.10%  
Gross liability for unrecognized tax benefits, excluding interest and penalties $ 25.3   $ 24.6
Liabilities for payment of interest and penalties related to its unrecognized tax benefits $ 4.8   $ 4.5