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Summary of Restricted Stock Unit's Activity (Detail) - Restricted Stock Units (RSUs) - $ / shares
12 Months Ended
Jan. 31, 2017
Jan. 31, 2016
Jan. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted, Shares 561,500 0 0
Vested, Shares 0   0
Forfeited, Shares (30,000)    
Non-vested awards outstanding at end of year, Shares 531,500    
Granted, Weighted average fair value $ 28.10    
Vested, Weighted average fair value 0 $ 39.06  
Forfeited, Weighted average fair value 26.78    
Non-vested awards outstanding at end of year, Weighted average fair value $ 28.17