Quarterly report pursuant to Section 13 or 15(d)

Stock Plans and Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail)

v2.4.0.8
Stock Plans and Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Stock-based compensation expense     $ 1,012 $ 49
Stock-based compensation expense 225 16 1,017 49
Research and development [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Stock-based compensation expense 73 5 256 16
General and administrative [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Stock-based compensation expense $ 152 $ 11 $ 761 $ 33