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Stock-Based Compensation and Shares Repurchases - Narrative (Details) - USD ($)
3 Months Ended 6 Months Ended 8 Months Ended
Nov. 30, 2017
Feb. 28, 2018
Feb. 28, 2017
Feb. 28, 2018
Jul. 31, 2017
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]          
Stock-based compensation recognized for modification $ 24,900,000        
2017 Share Repurchase Program          
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]          
Share repurchase program, amount authorized (up to)         $ 450,000,000
Shares repurchased       8,200,000  
Shares repurchased, value   $ 225,000,000   $ 225,000,000  
Share repurchase program, remaining authorized repurchase amount   $ 225,000,000   $ 225,000,000  
Time-based restricted stock units          
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]          
Award vesting period   3 years      
Restricted stock units awarded (in shares)   1,400,000 1,800,000    
Performance-based restricted stock units          
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]          
Award vesting period   3 years      
Restricted stock units awarded (in shares)   400,000 600,000    
Performance-based restricted stock units | Maximum          
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]          
Award vesting percentage   150.00%      
Market based restricted stock units          
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]          
Award vesting period   3 years      
Award vesting percentage   200.00%      
Restricted stock units awarded (in shares)   400,000 400,000    
Restricted stock awards          
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]          
Awards vested (in shares) 800,000        
Plan 2011          
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]          
Shares available for issuance under share based compensation plan   12,573,989   12,573,989