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Share-Based Compensation - Summary of Options Outstanding (Detail) - $ / shares
12 Months Ended
Jan. 31, 2017
Dec. 31, 2017
Jan. 31, 2016
Jan. 31, 2015
Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares outstanding, total 685,456   657,936 656,011 736,647
Outstanding, Weighted Average Exercise Price   $ 11.96      
Exercisable, Weighted Average Exercise Price   10.61      
Outstanding Remaining Contractual Life 6 years 1 month 6 days        
Number of shares exercisable, total 432,656        
Exercisable Remaining Contractual Life 4 years 8 months 12 days        
Range Three [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Outstanding Range of Exercise prices, Lower Limit $ 5.00        
Outstanding Range of Exercise prices, Upper Limit $ 10.00        
Outstanding, Number of shares 190,706        
Outstanding, Weighted Average Exercise Price   7.85      
Exercisable, Weighted Average Exercise Price   7.85      
Outstanding Remaining Contractual Life 3 years 10 months 24 days        
Exercisable, Number of shares 190,706        
Exercisable Remaining Contractual Life 3 years 10 months 24 days        
Range Four [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Outstanding Range of Exercise prices, Lower Limit $ 10.01        
Outstanding Range of Exercise prices, Upper Limit $ 15.00        
Outstanding, Number of shares 439,750        
Outstanding, Weighted Average Exercise Price   13.36      
Exercisable, Weighted Average Exercise Price   12.79      
Outstanding Remaining Contractual Life 6 years 7 months 6 days        
Exercisable, Number of shares 241,950        
Exercisable Remaining Contractual Life 5 years 3 months 18 days        
Range Five [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Outstanding Range of Exercise prices, Lower Limit $ 15.01        
Outstanding Range of Exercise prices, Upper Limit $ 20.00        
Outstanding, Number of shares 55,000        
Outstanding, Weighted Average Exercise Price   $ 15.07      
Outstanding Remaining Contractual Life 9 years 2 months 12 days