Securities Purchase Agreement - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Mar. 26, 2015	Sep. 08, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Nov. 17, 2014	Nov. 16, 2014
Changes In Equity And Comprehensive Income Line Items [Line Items]
Common stock par value per share			$ 0.001	$ 0.001
Aggregate gross proceeds from the issuance of Series C preferred stock and common stock			$ 0	$ 14,163	$ 0
Expense on fair value warrants			0	3,280	0
Proceeds from the exercise of warrants			$ 8,644	$ 0	$ 0
Common stock shares reserved for issuance			44,842,000	14,660,000
Common stock, shares authorized			150,000,000	100,000,000		100,000,000	50,000,000
Series C Preferred Stock
Changes In Equity And Comprehensive Income Line Items [Line Items]
Number of shares sold		87,196
Convertible preferred stock par value per share		$ 0.001
Price per share		$ 17.50
Aggregate gross proceeds from the issuance of Series C preferred stock and common stock		$ 14,400
Series C Preferred Stock, shares issued upon conversion into common stock		10
Beneficial conversion feature		$ 400
Series C Convertible Preferred Stock
Changes In Equity And Comprehensive Income Line Items [Line Items]
Common stock shares reserved for issuance		871,960
Common Stock
Changes In Equity And Comprehensive Income Line Items [Line Items]
Number of shares sold		7,363,334	2,158,000	7,363,000
Common stock par value per share		$ 0.001
Price per share		$ 1.75
Common stock warrants outstanding
Changes In Equity And Comprehensive Income Line Items [Line Items]
Warrants to purchase common stock sold (shares)		4,117,647
Exercise price per share		$ 2.26
2014 Warrant [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Proceeds from the exercise of warrants	$ 8,600
2014 Warrant [Member] | Common stock warrants outstanding
Changes In Equity And Comprehensive Income Line Items [Line Items]
Number of shares sold	3,824,600
Exercise price per share		$ 2.26
2015 Warrant [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Proceeds from the exercise of warrants	$ 3,500
2015 Warrant [Member] | Common stock warrants outstanding
Changes In Equity And Comprehensive Income Line Items [Line Items]
Warrants to purchase common stock sold (shares)	1,593,583
Exercise price per share	$ 5.50