Preferred Stock and Stockholders' Equity - Common Stock Warrants Narrative (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended			1 Months Ended
	Jul. 27, 2012	Jul. 18, 2011	Dec. 31, 2012	Jun. 30, 2011 Oxford/SVB [Member]	Dec. 31, 2011 Oxford/SVB [Member]	Dec. 31, 2012 Cowen Royalty [Member]	Dec. 31, 2011 Cowen Royalty [Member]
Schedule Of Common Stock [Line Items]
Shares of common stock exercisable through warrants	15,784,200			26,455
Warrants exercise price (in usd per share)	$ 2.50			$ 3.78
Warrants expiry date	July 27, 2017
Term of common stock warrant exercisable	5 years	10 years		7 years
Fair value of warrant liabilities			$ 9,308			$ 185	$ 345
Warrant exercisable to Healthcare Royalty, shares		225,000		26,455
Warrants exercisable date	Jul. 27, 2013
Investment Warrants, Exercise Price		$ 9.00
Debt discount					$ 76