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Stock-Based Compensation Expense and Shareholders' Equity (Details 3) - TSR PSUs
3 Months Ended
Oct. 31, 2019
Oct. 31, 2018
Summary of assumptions for fair value of employee stock option estimates    
Expected term (in years) 2 years 10 months 24 days 2 years 10 months 17 days
Risk-free interest rate 1.50% 2.80%
Expected volatility of the Company 28.40% 27.20%
Average expected volatility of the peer companies in the S&P Index 37.00% 33.00%
Expected dividend yield 0.00% 0.00%