Revenue - Summary of Company's Revenue (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
Deferred Revenue Disclosure [Abstract]        
Government grants   $ 151 $ 418 $ 516
Research and development agreements 3,365 4,415 6,971 8,315
Total $ 3,365 $ 4,566 $ 7,389 $ 8,831