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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended
Apr. 30, 2018
Apr. 30, 2017
Aug. 22, 2017
Feb. 23, 2015
Equity, Class of Treasury Stock [Line Items]        
Common shares authorized for repurchase, shares 0 0   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 $ 5,047      
Employee Stock        
Equity, Class of Treasury Stock [Line Items]        
Stock repurchased and retired during period, common shares 138,310 43,423    
Stock repurchased and retired during period, total cost $ 5,047 $ 1,142