Common Stock Warrants - Additional Informational (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended						1 Months Ended
	Jul. 27, 2012	Jul. 18, 2011	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Healthcare Royalty	Dec. 31, 2012 Healthcare Royalty	Jun. 30, 2011 Oxford/SVB [Member]	Dec. 31, 2011 Oxford/SVB [Member]
Schedule Of Common Stock [Line Items]
Shares of common stock exercisable through warrants	15,784,200						26,455
Warrants exercisable date	Jul. 27, 2013
Warrants exercise price per share	$ 2.50						$ 3.78
Warrants expiry date	July 27, 2017
Term of common stock warrant exercisable (years)	5 years	10 years					7 years
Fair value of warrant liabilities			$ 12,045	$ 9,308	$ 228	$ 185
Warrant exercisable to Healthcare Royalty, shares		225,000
Warrant exercisable to Healthcare Royalty, price per share (usd per share)		$ 9.00
Unamortized debt discount								$ 76