Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation and Stock Incentive Plans - Additional Information (Detail)

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Stock-Based Compensation and Stock Incentive Plans - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
1 Months Ended 6 Months Ended 12 Months Ended
May 31, 2012
Jul. 31, 2013
Jan. 31, 2012
Jul. 20, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]        
Share-based compensation arrangement by share-based payment award, number of shares authorized   5,300,000   2,800,000
Increased number of shares authorized for issuance   2,500,000    
Share based compensation arrangement by share based payment award vesting limit per participant   1,250,000 500,000  
Share based compensation arrangement by share based payment award maximum number of shares per participant   1,250,000 500,000  
Share-based compensation arrangement by share-based payment award, description   Option awards may be granted to employees at an exercise price per share of not less than 100% of the fair market value per common share on the date of the grant.    
Share-based compensation arrangement by Share-based payment award, award vesting period   3 years    
Share based compensation arrangement by share based payment award, award expiration period   7 years    
Share-based compensation arrangement by share-based payment award, options, grants in period, gross 875,000 875,000    
Share-based compensation arrangement by share-based payment award, options, vested and expected to vest, outstanding, number   583,334    
Unvested options   291,666    
Share-based compensation arrangement by share-based payment award, options, vested in period, fair value $ 3.3 $ 3.3