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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 6 Months Ended 12 Months Ended
Sep. 09, 2015
Jul. 31, 2015
Jul. 31, 2015
Jul. 31, 2014
Jan. 31, 2015
Feb. 23, 2015
May. 27, 2014
Equity, Class of Treasury Stock [Line Items]              
Common shares authorized for repurchase, shares           20,000,000 10,000,000
Stock repurchased and retired during period, common shares   4,755,672 4,755,672        
Stock repurchased and retired during period, total cost   $ 170,792 $ 170,792        
Average cost per share   $ 35.91 $ 35.91        
Additional paid-in-capital reduction related to shares repurchased     $ 0        
Retained earnings reduction related to shares repurchased     $ (201,773)        
Subsequent Event              
Equity, Class of Treasury Stock [Line Items]              
Stock repurchased and retired during period, common shares 1,300,000            
Stock repurchased and retired during period, total cost $ 40,023            
Average cost per share $ 30.79            
Employee Stock              
Equity, Class of Treasury Stock [Line Items]              
Stock repurchased and retired during period, common shares     181,890 1,690      
Stock repurchased and retired during period, total cost     $ 8,017 $ 61      
New Share Repurchase Program              
Equity, Class of Treasury Stock [Line Items]              
Stock repurchased and retired during period, common shares   1,879,492 2,281,469   7,718,531    
Stock repurchased and retired during period, total cost   $ 65,520 $ 82,826   $ 258,160    
Average cost per share   $ 34.86 $ 36.30   $ 33.45