Preferred Stock - Additional Information (Detail) - USD ($)			1 Months Ended				12 Months Ended
	Jan. 31, 2014	Dec. 11, 2013	May. 31, 2014	Mar. 31, 2014	Jan. 31, 2014	Jul. 31, 2006	Dec. 31, 2015	Dec. 31, 2014	May. 07, 2014
Temporary Equity [Line Items]
Preferred shares authorized (in shares)							5,000,000	5,000,000	5,000,000
Preferred shares par value (USD per share)							$ 0.001	$ 0.001	$ 0.001
Preferred shares issued (in shares)							0	0
Preferred shares outstanding (in shares)							0	0
Automatic conversion trigger (at least)				$ 20,000,000
Conversion of preferred stock (in shares)			1,691,884					1,691,884
Number of warrants issued to purchase common stock (in shares)							14,033	14,033
Exercise price of warrants (in dollars per share)			$ 0.20
Other (expense) income related to fair value adjustment of long term derivative liability								$ 10,442,000
Excess of fair value of warrants over proceeds					$ 362,000			362,000
Proceeds from sale of preferred stock							$ 0	544,000
Series C-1 Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)						196,923
Exercise price of warrants (in dollars per share)						$ 3.25
Fair value of warrant on issuance date						$ 459,000
Other (expense) income related to fair value adjustment of long term derivative liability							$ 0	$ 37,000
Common Stock [Member]
Temporary Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)							14,033
Exercise price of warrants (in dollars per share)							$ 45.61
Series D-2 Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)	19,048	87,532			19,048
Exercise price of warrants (in dollars per share)	$ 0.20	$ 0.20			$ 0.20
Fair value of warrant on issuance date	$ 906,000	$ 4,214,000
Excess of fair value of warrants over proceeds	$ 362,000	$ 1,714,000
Temporary equity, shares issued (in shares)	388,641				388,641
Temporary equity issue price per share (in dollars per share)	$ 1.40				$ 1.40
Proceeds from sale of preferred stock	$ 544,000