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Stock-Based Compensation - Stock Option Assumptions (Detail) - $ / shares
6 Months Ended
Jan. 31, 2018
Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected term 6 years 26 days 6 years 1 month 10 days
Expected volatility 26.52% 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 $ 35.13
Options, Grants in Period, Weighted Average Exercise Price 36.85 35.13
Weighted-average fair value of options granted during the period $ 7.96 $ 7.56