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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Oct. 31, 2019
Oct. 31, 2018
Oct. 31, 2019
Oct. 31, 2018
Jun. 04, 2019
Aug. 22, 2017
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 26,333,957   26,333,957      
Stock repurchased and retired during period, total cost $ 145 $ 61,775 $ 222,995 $ 67,699    
Employee Stock            
Equity, Class of Treasury Stock [Line Items]            
Stock repurchased and retired during period, common shares     184,402 252,619    
Stock repurchased and retired during period, total cost     $ 5,574 $ 10,187