Annual report pursuant to Section 13 and 15(d)

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

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Equity Incentive Plans and Stock Based Compensation - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of shares issued and outstanding 5.00%    
Increase in authorized shares 1,250,000    
Aggregate intrinsic value of options outstanding $ 10,500,000    
Aggregate intrinsic value of options exercisable 8,600,000    
Options vested and expected to vest 6,483,107    
Aggregate intrinsic value of options vested and expected to vest 10,500,000    
Weighted average remaining contractual life of options vested and expected to vest 7 years 6 months 18 days    
Weighted average exercise price of options vested and expected to vest $ 3.65    
Intrinsic value of stock options exercised 500,000 1,700,000 6,000
Cash received from stock option exercises 100,000 600,000 14,000
Tax benefit realized upon exercise of option 0 0 0
Offering period 24 months    
Purchase period 6 months    
Common stock purchased by employees 167,245 150,677  
Common stock purchased under Purchase Plan at average price $ 1.69 $ 1.18  
Amount withheld by plan participants to purchase stock 300,000    
Discount available to eligible employees related to employee stock purchase plan 85.00%    
Shares authorized and available for issuance under the ESPP 235,896    
Stock-based compensation expense 4,922,000 3,010,000 1,039,000
Non-employees stock-based compensation expense 100,000 200,000 100,000
2004 Equity Incentive Plan [Member]
      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of fair market value 100.00%    
Terms of stock options granted 10 years    
Terms of stock options vested 4 years    
Employee Stock-based Compensation Expense [Member]
      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock-based compensation expense 4,800,000 2,800,000 800,000
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans $ 10,300,000    
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition 2 years 4 months 24 days