License Obligations - Arcion License Agreement - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential payments upon filing and acceptance	$ 10.0
Increase in milestone payments	8
U.S. [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
U.S. [Member] | Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone Sales	200
Milestone payments receivable from sublicenses	70
Arcion Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential payments upon filing and acceptance	2.5
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.
Arcion Agreement [Member] | Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential milestone payments upon FDA approval	17.5
Arcion Agreement [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential milestone payments upon FDA approval	$ 35.0