XML 20 R37.htm IDEA: XBRL DOCUMENT v2.4.0.8
Stock-Based Compensation - Summary of Activity under Company's Stock Option Plans (Detail) (USD $)
 3 Months Ended 12 Months Ended
Apr. 30, 2014
Jan. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Shares, Outstanding, Beginning balance 916,150  
Shares, Granted 180,500  
Shares, Exercised (83,500)  
Shares, Outstanding, Ending balance 1,013,150 916,150
Shares, Exercisable 600,650 613,150
Weighted Average Exercise Price, Outstanding, Beginning balance $ 17.36  
Weighted Average Exercise Price, Granted $ 27.09  
Weighted Average Exercise Price, Exercised $ 13.50  
Weighted Average Exercise Price, Outstanding, Ending balance $ 19.41 $ 17.36
Weighted Average Exercise Price, Exercisable $ 15.75 $ 15.40
Weighted Average Remaining Contract Term, Granted     
Weighted Average Remaining Contract Term, Exercised     
Weighted Average Remaining Contract Term, Outstanding 6 years 9 months 4 days 6 years 15 days
Weighted Average Remaining Contract Term, Exercisable 5 years 11 months 23 days 5 years 1 month 2 days
Weighted Average Fair Value, Granted     
Weighted Average Fair Value, Exercised     
Weighted Average Fair Value, Outstanding, Beginning balance $ 5.65 $ 5.58
Weighted Average Fair Value, Exercisable $ 5.81 $ 6.15