Significant Agreements - Schedule of Assumptions Used to Value Shares of Common Stock Issuable Pursuant to Warrant (Detail) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Mar. 08, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Warrant or Right [Line Items]
Estimated Volatility			71.40%	69.92%	70.36%
Risk-free interest rate			1.41%	1.73%	1.91%
Estimated Dividend Yield			0.00%	0.00%	0.00%
Estimated Remaining Contractual Life (in years)			5 years 10 months 6 days	5 years 10 months 21 days	5 years 11 months 16 days
Common Stock Warrant [Member]
Class of Warrant or Right [Line Items]
Revaluation Date of Warrant	Mar. 08, 2016	Dec. 31, 2015
Total Shares of Common Stock Issuable Under the Warrant	357,840	277,486		277,486
Average Exercise Price	$ 1.54	$ 1.54		$ 1.54
Fair Value of Common Stock	$ 13.55	$ 11.13		$ 11.13
Estimated Volatility	69.00%	73.00%
Risk-free interest rate	1.82%	2.15%
Estimated Dividend Yield	0.00%	0.00%
Estimated Remaining Contractual Life (in years)	10 years	8 years 22 days
Fair Value of Warrant Liability	$ 4,551	$ 2,848		$ 2,848