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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ in Thousands
 9 Months Ended
Oct. 31, 2018
Oct. 31, 2017
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 16,402,153      
Stock repurchased and retired during period, total cost $ 67,699      
Employee Stock        
Equity, Class of Treasury Stock [Line Items]        
Stock repurchased and retired during period, common shares 252,619 92,404    
Stock repurchased and retired during period, total cost $ 10,187 $ 2,180