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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jul. 31, 2020
Jul. 31, 2019
Jul. 31, 2020
Jul. 31, 2019
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 25,851,954   25,851,954      
Stock repurchased and retired during period, total cost $ 22 $ 146,225 $ 10,778 $ 222,850    
Employee Stock            
Equity, Class of Treasury Stock [Line Items]            
Stock repurchased and retired during period shares     155,734 178,064    
Stock repurchased and retired during period, total cost     $ 3,742 $ 5,429