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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ in Thousands
 9 Months Ended
Oct. 31, 2017
Oct. 31, 2016
Aug. 22, 2017
Feb. 23, 2015
Equity, Class of Treasury Stock [Line Items]        
Common shares authorized for repurchase, shares     20,000,000 20,000,000
Remaining common shares authorized for repurchase, shares 17,902,153      
Stock repurchased and retired during period, total cost $ 159,224      
Employee Stock        
Equity, Class of Treasury Stock [Line Items]        
Stock repurchased and retired during period, common shares 92,404 55,683    
Stock repurchased and retired during period, total cost $ 2,180 $ 2,049