Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Additional Information (Detail)

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Stock-Based Compensation - Additional Information (Detail) (USD $)
 3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Stock options granted 0 0 35,000 100,000
Weighted-average grant date fair value $ 0.00 $ 0.00 $ 3.41 $ 1.03
Stock options vested     50,533  
Stock options forfeited     56,050  
Stock options exercised     31,533  
2012 Equity Incentive Plan [Member]
        
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Liability and expense related to equity incentive plan $ 1,487,801      
Grant date fair value, shares expected to be awarded 422,359