Arcion License Agreement - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common stock locking period	9 months
Milestone payments increased	$ 8,000,000
Research and development expense	53,326,777	35,365,662	20,805,177
US [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential Payments upon achieving certain pre-determined sales thresholds in the U.S	60,000,000
US [Member] | Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone Sales	200,000,000
Milestone payment receivable from sublicenses	70,000,000
Arcion License Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Share issued to Arcion	500,516
Fair market value of unregistered shares issued	2,100,000
Potential payments upon filing and acceptance	2,500,000
Royalty term description	The royalty term for any given country is the later of (i) the first date there are no valid claims against any Arcion patent, (ii) expiration of patent exclusivity or (iii) tenth anniversary of the first commercial sale.
Research and development expense	2,100,000
Arcion License Agreement [Member] | Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential milestone payment upon FDA approval	17,500,000
Arcion License Agreement [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential milestone payment upon FDA approval	$ 35,000,000