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Stock-Based Compensation - Stock Option Assumptions (Detail) (USD $)
3 Months Ended
Oct. 31, 2014
Oct. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected term 6 years 0 months 17 days 5 years 11 months
Expected volatility 30.27% 37.41%
Expected dividend yield 2.48% 2.36%
Risk-free interest rate 1.91% 1.78%
Weighted-average market value of underlying stock at grant date $ 22.66 $ 31.07
Weighted average exercise price (USD per share) $ 22.66 $ 31.07
Weighted-average fair value of options granted during the period $ 6.10 $ 9.18