Controlled Equity Offering and Public Offering of Common Stock - Schedule of Total Sales under Sales Agreement (Detail) - Cantor Fitzgerald & Co. [Member] $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares
Sale And Issue Of Shares Under Agreement [Line Items]
Total shares of common stock sold | shares	2,014,300
Average price per share | $ / shares	$ 3.25
Gross proceeds	$ 6,546
Commissions earned by Cantor	197
Other issuance costs	$ 259