Revenue - Summary of Company's Revenue (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Deferred Revenue Disclosure [Abstract]        
Government grants $ 253 $ 365 $ 418 $ 365
Research and development agreements 2,206 2,412 3,606 3,900
Total $ 2,459 $ 2,777 $ 4,024 $ 4,265