Embedded Derivatives and Derivative Warrant Liabilities - Additional Information (Detail) - USD ($)		1 Months Ended										3 Months Ended
	Dec. 11, 2015	Feb. 28, 2017	Sep. 30, 2016	Jun. 30, 2016	Apr. 30, 2016	Dec. 31, 2015	May 31, 2015	Feb. 28, 2015	Aug. 31, 2014	Dec. 31, 2013	Jul. 31, 2012	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	May 31, 2016	Apr. 01, 2016
Derivative [Line Items]
Estimated fair value of the embedded derivatives												$ 0		$ 0
Additional purchase of common stock shares												17,106,683
Derivative warrant liability fair value												$ 4,942,000		$ 2,698,000
Proceeds from the exercise of warrants												$ 2,000	$ 65,000
Series A
Derivative [Line Items]
Additional purchase of common stock shares								110,833				110,833
Warrant , exercise price												$ 1.90
Series B
Derivative [Line Items]
Additional purchase of common stock shares								110,883				110,833
Series C
Derivative [Line Items]
Additional purchase of common stock shares							21,500					21,500
Warrant , exercise price												$ 9.59
Series D
Derivative [Line Items]
Additional purchase of common stock shares						502,500						502,500
Warrant , exercise price												$ 2.00
Series E
Derivative [Line Items]
Additional purchase of common stock shares						400,000						400,000
Series F
Derivative [Line Items]
Additional purchase of common stock shares					514,644							514,644
Number of securities called by each warrant					1
Warrant , exercise price												$ 2.00
Series H
Derivative [Line Items]
Additional purchase of common stock shares					1,029,286							1,029,286
Number of securities called by each warrant					1
Series G
Derivative [Line Items]
Additional purchase of common stock shares					328,571							328,571
Number of securities called by each warrant					1
Series I
Derivative [Line Items]
Additional purchase of common stock shares			712,503									712,503
Number of securities called by each warrant			1
Warrant , exercise price												$ 11.00
Series J
Derivative [Line Items]
Additional purchase of common stock shares			185,000									185,000
Number of securities called by each warrant			1
Series K
Derivative [Line Items]
Additional purchase of common stock shares		6,250,000										6,250,000
Number of securities called by each warrant		1
Warrant , exercise price												$ 2.35
Series L
Derivative [Line Items]
Additional purchase of common stock shares		570,000										570,000
Number of securities called by each warrant		1
Common Stock Units Issued												155,000
Proceeds from the exercise of warrants												$ 2,000
Warrant , exercise price												$ 0.01
Series M
Derivative [Line Items]
Additional purchase of common stock shares		6,250,000										6,250,000
Number of securities called by each warrant		1
Warrant , exercise price												$ 2.35
375,000 Exercisable Series H
Derivative [Line Items]
Shares warrants exercisable															375,000
Warrant , exercise price					$ 15.00										$ 6.00
150,000 Exercisable Series H
Derivative [Line Items]
Shares warrants exercisable				150,000
Warrant , exercise price				$ 8.40												$ 15.00
100,000 Exercisable Series H
Derivative [Line Items]
Shares warrants exercisable				100,000
Warrant , exercise price				$ 10.40												$ 15.00
50,000 Exercisable Series H
Derivative [Line Items]
Shares warrants exercisable				50,000
Warrant , exercise price				$ 10.40
Series D Warrant Agreement Amendment
Derivative [Line Items]
Shares warrants exercisable				208,370
Warrant , exercise price	$ 2.00			$ 3.50
Warrants, exercise date	Jun. 11, 2016			Jun. 08, 2016
2013 Warrants
Derivative [Line Items]
Additional purchase of common stock shares										71,013		71,013
Warrant , exercise price												$ 15.84
2014 Warrants
Derivative [Line Items]
Additional purchase of common stock shares									50,000			50,000
Warrant , exercise price												$ 11.98
July 2022 Notes
Derivative [Line Items]
Percentage of convertible senior notes embedded derivatives											7.50%
7.5% convertible senior notes, maturity date											2022
2022 notes, conversion date											Jul. 01, 2017