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Stock-Based Compensation - Additional Information (Detail) (USD $)
Share data in Millions, unless otherwise specified
3 Months Ended
Nov. 30, 2012
Nov. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Recognition of stock-based compensation expense $ 18,803,000 $ 18,665,000
Stock-based compensation expense, tax effect 200,000 400,000
Time-based restricted stock units
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award vesting period 3 years  
Restricted stock units awarded 1.8  
Performance-based restricted stock units
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award vesting period 3 years  
Restricted stock units awarded 1.7  
Performance-based restricted stock units | Possibility One | Maximum
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award vesting percentage 100.00%  
Performance-based restricted stock units | Possibility Two | Maximum
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award vesting percentage 150.00%  
Restricted Stock
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Unrecognized compensation related to share-based compensation costs $ 97,900,000  
Unrecognized compensation related to share-based compensation costs, weighted average period of recognition 1 year 6 months