Annual report pursuant to Section 13 and 15(d)

Common Stock - Summary of Share-Based Compensation Expense (Detail)

v2.4.0.8
Common Stock - Summary of Share-Based Compensation Expense (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation $ 2,834 $ 2,175 $ 1,188
Research and development [Member]
      
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation 1,296 899 509
General and administrative [Member]
      
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation $ 1,538 $ 1,276 $ 679