Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Stock-Based Compensation Expense (Detail)

v2.4.0.8
Stock Based Compensation - Stock-Based Compensation Expense (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]    
Stock-based compensation expense $ 1,266 $ 1,053
Research and Development [Member]
   
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]    
Stock-based compensation expense 671 534
General and Administrative [Member]
   
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]    
Stock-based compensation expense $ 595 $ 519