Significant Agreements - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended		1 Months Ended
	May 31, 2009 Charley's Fund Agreement	Oct. 30, 2007 Charley's Fund Agreement	Dec. 31, 2012 Charley's Fund Agreement	Nov. 30, 2012 European Union Three Years	Nov. 30, 2012 European Union January 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate amount of research grant			$ 3,400,000	$ 2,500,000
Revenue recognized from research grant			60,000		635,000
Research and development grant awarded	5,000,000	2,450,000
Deferred grant payment			$ 3,300,000