Common Stock Warrants - Additional Informational (Detail) (USD $)	0 Months Ended		1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Jul. 27, 2012	Jul. 18, 2011	Jul. 18, 2011	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Schedule Of Common Stock [Line Items]
Shares of common stock exercisable through warrants	15,784,200
Warrants exercise price per share	$ 2.50
Warrants expiry date	July 27, 2017
Term of common stock warrant exercisable (years)	5 years	10 years
Proceeds from warrant exercises				$ 1,163,000	$ 1,163,000	$ 259,000
Fair value of warrant liabilities				11,735,000	11,735,000	30,849,000
Warrant exercisable to Healthcare Royalty, shares		225,000	225,000
Warrant exercisable to Healthcare Royalty, price per share (usd per share)		$ 9.00
Healthcare Royalty
Schedule Of Common Stock [Line Items]
Fair value of warrant liabilities				$ 220,000	$ 220,000	$ 492,000
Common stock warrants
Schedule Of Common Stock [Line Items]
Warrants exercised				465,250	465,250	103,500