Common Stock Warrants - Additional Informational (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		9 Months Ended	12 Months Ended
	Jul. 27, 2012	Jul. 31, 2012	Jul. 31, 2011	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Common Stock [Line Items]
Shares of common stock exercisable through warrants				1,901,931
Warrants exercise price per share	$ 20.00
Term of common stock warrant exercisable (years)	5 years		10 years
Proceeds from warrant exercises					$ 1,163
Fair value of warrant liabilities				$ 5,840	4,978
Warrant exercisable to Healthcare Royalty, shares			28,125
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				$ 114	$ 115
Common stock warrants
Schedule Of Common Stock [Line Items]
Warrants exercised					58,156
IPO
Schedule Of Common Stock [Line Items]
Number of shares issued in public offering		1,973,000