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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Jan. 31, 2018
Jan. 31, 2017
Jan. 31, 2016
Aug. 22, 2017
Feb. 23, 2015
Equity, Class of Treasury Stock [Line Items]          
Common shares authorized for repurchase, shares         20,000,000
Additional common shares authorized for repurchase, shares       20,000,000  
Remaining common shares authorized for repurchase, shares 17,902,153        
Stock repurchased and retired during period, total cost $ (159,226) $ (47,839) $ (475,424)    
Employee Stock          
Equity, Class of Treasury Stock [Line Items]          
Stock repurchased and retired during period, common shares 92,455 55,769      
Stock repurchased and retired during period, total cost $ 2,182 $ 2,052