Derivative Instruments - Summary of Assumptions Used in Computing Fair Value (Detail) - $ / shares	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Convertible Notes [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value assumption stock price	$ 0.68	$ 0.28
Fair value assumption conversion price	$ 1.25	$ 1.25
Expected volatility rate	143.00%	140.00%
Remaining term of expected volatility	6 years 3 months	7 years 3 months
Risk-free interest rate	1.95%	1.97%
Expected dividend yield	0.00%	0.00%
Reimbursement Notes [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value assumption stock price	$ 0.68	$ 0.28
Fair value assumption conversion price	$ 0.50	$ 0.50
Expected volatility rate	143.00%	140.00%
Remaining term of expected volatility	6 years 3 months	7 years 3 months
Risk-free interest rate	1.95%	1.97%
Expected dividend yield	0.00%	0.00%
Bridge Notes [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value assumption stock price	$ 0.68	$ 0.28
Fair value assumption conversion price	$ 0.50	$ 0.50
Expected volatility rate	143.00%	140.00%
Remaining term of expected volatility	6 years 3 months	7 years 3 months
Risk-free interest rate	1.95%	1.97%
Expected dividend yield	0.00%	0.00%
Amended and Restated June 2010 Warrants [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value assumption stock price	$ 0.68	$ 0.28
Fair value assumption conversion price	$ 0.50	$ 0.50
Expected volatility rate	136.00%	160.00%
Remaining term of expected volatility	3 years 6 months 7 days	4 years 6 months 7 days
Risk-free interest rate	1.42%	1.51%
Expected dividend yield	0.00%	0.00%
Warrants [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value assumption stock price	$ 0.68	$ 0.28
Fair value assumption conversion price	$ 0.50	$ 0.50
Expected volatility rate	141.00%	161.00%
Remaining term of expected volatility	3 years 6 months 7 days	4 years 6 months 7 days
Risk-free interest rate	1.31%	1.65%
Expected dividend yield	0.00%	0.00%
August 2010 Investor Warrants [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value assumption stock price		$ 0.28
Fair value assumption conversion price		$ 1.26
Expected volatility rate		116.00%
Remaining term of expected volatility		7 months 24 days
Risk-free interest rate		0.12%
Expected dividend yield		0.00%
July 2011 Investor Warrants [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value assumption stock price	$ 0.68	$ 0.28
Fair value assumption conversion price	$ 1.09	$ 1.09
Expected volatility rate	88.00%	122.00%
Remaining term of expected volatility	6 months 4 days	1 year 6 months 4 days
Risk-free interest rate	0.49%	0.67%
Expected dividend yield	0.00%	0.00%
2013 Restructuring Warrants [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value assumption stock price	$ 0.68	$ 0.28
Fair value assumption conversion price	$ 0.50	$ 0.50
Expected volatility rate	141.00%	161.00%
Remaining term of expected volatility	3 years 6 months 7 days	4 years 6 months 7 days
Risk-free interest rate	1.31%	1.65%
Expected dividend yield	0.00%	0.00%

Fair value assumption conversion price.

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- Definition

Remaining term of expected volatility.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

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Risk-free interest rate assumption used in valuing an instrument.

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- Definition

Price of a single share of a number of saleable stocks of a company.

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