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Stock-Based Compensation - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Jul. 31, 2013
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Options, granted   1,455,150    
Tax benefit recognized related to share-based compensation cost   $ 0    
Unrecognized compensation cost   $ 14,300,000    
Unrecognized compensation cost, weighted-average recognized period   2 years 7 months 10 days    
Total share-based compensation expense   $ 6,278,000 $ 4,926,000 $ 1,145,000
Exercise Prices that Were Less than the Estimated per Share Value [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Options, granted       101,487
2004 Stock Option Plan and 2013 Equity Incentive Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share available for grant   5,446,915    
Stock options grant period, years   10 years    
Stock options vesting period and exercisable period, years   4 years    
Employee Stock Purchase Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share available for grant   332,704    
Offering period description   The offering periods generally start with the first trading day on or after March 1 and September 1 of each year and end on the first trading day on or after March 1 and September 1 of the following year, approximately 12 months later. Within each offering period, shares will be purchased each 6 months on an exercise date. The first offering period began in August 2013.    
Length of offering period, in months 12 months      
Length of purchase periods, in months 6 months      
Shares issued   136,078 141,386 0
Common stock reserved for issuance   610,166    
Total share-based compensation expense   $ 435,000 $ 394,000  
Employee Stock Purchase Plan [Member] | Minimum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Contribution percentage of purchase shares on participants eligible compensation   0.00%    
Employee Stock Purchase Plan [Member] | Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Contribution percentage of purchase shares on participants eligible compensation   10.00%    
Employee Stock Purchase Plan [Member] | First Trading Day of Offering Period [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Purchase price percentage of fair market value of shares   85.00%    
Employee Stock Purchase Plan [Member] | Exercise Date [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Purchase price percentage of fair market value of shares   85.00%