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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended
Jun. 09, 2017
Apr. 30, 2017
Apr. 30, 2016
Feb. 23, 2015
Equity, Class of Treasury Stock [Line Items]        
Common shares authorized for repurchase, shares       20,000,000
Remaining common shares authorized for repurchase, shares   5,995,059    
Stock repurchased and retired during period, total cost   $ 1,142    
Subsequent Event | New Share Repurchase Program        
Equity, Class of Treasury Stock [Line Items]        
Stock repurchased and retired during period, common shares 500,000      
Stock repurchased and retired during period, total cost $ 9,455      
Average cost per share $ 18.91      
Employee Stock        
Equity, Class of Treasury Stock [Line Items]        
Stock repurchased and retired during period, common shares   43,423 0  
Stock repurchased and retired during period, total cost   $ 1,142