Warrant Liability - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Jul. 05, 2016
Warrant Liability [Line Items]
Derivative Liability, Fair Value, Gross Liability					$ 2,900	$ 4,600
Increase (Decrease) in Derivative Liabilities			$ 2,400
Gain (Loss) on Extinguishment of Debt	$ 0	$ 0	(440)	$ 0
Reclassified to equity			$ (175)
Health care Institutional Investors
Warrant Liability [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	2,941,176		2,941,176
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 2.30		$ 2.30
Hc Wainwright Co Llc
Warrant Liability [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	250,000		250,000
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 2.46		$ 2.46