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Stock-Based Compensation - Stock Option Assumptions (Detail) - $ / shares
3 Months Ended
Oct. 31, 2017
Oct. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]    
Expected term (in years) 6 years 26 days 6 years 1 month 9 days
Expected volatility 28.19% 29.43%
Expected dividend yield 2.72% 2.70%
Risk-free interest rate 1.96% 1.26%
Weighted-average market value of underlying stock at grant date $ 36.85 $ 35.14
Options, Grants in Period, Weighted Average Exercise Price 36.85 35.14
Weighted-average fair value of options granted during the period $ 7.96 $ 7.56