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Stock-Based Compensation - Summary of Activity under Company's Stock Option Plans (Detail) (USD $)
 9 Months Ended 12 Months Ended
Oct. 31, 2014
Jan. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]    
Shares, Outstanding, Beginning balance 916,150  
Shares, Granted 220,500  
Shares, Exercised (243,300)  
Shares, Outstanding, Ending balance 893,350 916,150
Shares, Exercisable 597,850 613,150
Weighted Average Exercise Price, Outstanding, Beginning balance $ 17.36  
Weighted Average Exercise Price, Granted $ 28.84  
Weighted Average Exercise Price, Exercised $ 15.96  
Weighted Average Exercise Price, Outstanding, Ending balance $ 20.57 $ 17.36
Weighted Average Exercise Price, Exercisable $ 16.73 $ 15.40
Weighted Average Remaining Term, Granted 0 years  
Weighted Average Remaining Term, Exercised 0 years  
Weighted Average Remaining Term, Outstanding 6 years 6 months 7 days 6 years 15 days
Weighted Average Remaining Term, Exercisable 5 years 9 months 7 days 5 years 1 month 2 days
Weighted Average Fair Value, Granted $ 0  
Weighted Average Fair Value, Exercised $ 0  
Weighted Average Fair Value, Outstanding, Beginning balance $ 5.87 $ 5.58
Weighted Average Fair Value, Exercisable $ 5.58 $ 6.15