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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Apr. 30, 2015
Jan. 31, 2016
Jan. 31, 2015
Feb. 23, 2015
May. 27, 2014
Aug. 27, 2013
Equity, Class of Treasury Stock [Line Items]            
Common shares authorized for repurchase, shares       20,000,000 10,000,000 10,000,000
Stock repurchased and retired during period, common shares 9,699,700 12,680,241        
Stock repurchased and retired during period, total cost $ 353,315 $ 382,478        
Average cost per share $ 36.43 $ 30.16        
Additional paid-in-capital reduction related to shares repurchased   $ 0        
Retained earnings reduction related to shares repurchased   $ (407,206)        
Employee Stock            
Equity, Class of Treasury Stock [Line Items]            
Stock repurchased and retired during period, common shares   247,124 111,563      
Stock repurchased and retired during period, total cost   $ 10,120 $ 3,947      
New Share Repurchase Program            
Equity, Class of Treasury Stock [Line Items]            
Stock repurchased and retired during period, common shares   2,281,469 7,718,531      
Stock repurchased and retired during period, total cost   $ 82,826 $ 258,160      
Average cost per share   $ 36.30 $ 33.45