Common Stock Warrant Liability - Additional Informational (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		9 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Sep. 30, 2016	Dec. 31, 2015	Jul. 27, 2012
Schedule Of Common Stock [Line Items]
Shares of common stock exercisable through warrants			1,901,918
Warrants exercise price per share (usd per share)					$ 20.00
Fair value of warrant liabilities			$ 968	$ 6,069
Warrant exercisable to Healthcare Royalty, shares		28,125
Term of common stock warrant exercisable		10 years
Warrant exercisable to Healthcare Royalty, price per share (usd per share)		$ 72.00
Healthcare Royalty
Schedule Of Common Stock [Line Items]
Fair value of warrant liabilities			$ 80	$ 127
IPO
Schedule Of Common Stock [Line Items]
Number of shares issued in public offering	1,973,025