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Stock-Based Compensation and Shares Repurchases - Narrative (Details) - USD ($)
6 Months Ended
Feb. 28, 2019
Feb. 28, 2018
Jun. 30, 2018
2018 Share Repurchase Program      
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]      
Share repurchase program, amount authorized (up to)     $ 350,000,000
Shares repurchased 13,900,000    
Shares repurchased, value $ 350,000,000    
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) 1,600,000 1,400,000  
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) 400,000 400,000  
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  
Plan 2011      
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]      
Shares available for issuance under share based compensation plan 11,933,647