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Stock-Based Compensation - Additional Information (Detail) (USD $)
Share data in Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Feb. 28, 2014
Feb. 28, 2013
Feb. 28, 2014
Feb. 28, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Recognition of stock-based compensation expense $ 14,652,000 $ 16,274,000 $ (7,934,000) $ 33,186,000
Reversal to stock-based compensation expense     38,400,000  
Stock-based compensation expense, tax (expense) benefit 500,000 200,000 500,000 400,000
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 1.9
Performance-based restricted stock units
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted stock units awarded     1.6 1.7
Performance-based restricted stock units | Minimum
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award vesting period     3 years  
Performance-based restricted stock units | Maximum
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award vesting period     5 years  
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 stock-based compensation expense related to restricted stock awards $ 68,200,000   $ 68,200,000  
Unrecognized stock-based compensation expense related to restricted stock awards, weighted average period of recognition     1 year 7 months 6 days