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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Jan. 31, 2017
Jan. 31, 2016
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
Remaining common shares authorized for repurchase, shares 5,995,059        
Stock repurchased and retired during period, total cost $ 47,839 $ 475,424 $ 615,421    
Employee Stock          
Equity, Class of Treasury Stock [Line Items]          
Stock repurchased and retired during period, common shares 55,769 247,124      
Stock repurchased and retired during period, total cost $ 2,052 $ 10,120