Warrant and derivative Liability Issued by Black Scholes Option Pricing Model (Detail) (USD $)	6 Months Ended	12 Months Ended
Jun. 30, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of underlying stock per share	$ 0.31	$ 3.00
Risk-free interest rate		1.48%
Expected term		8 years 9 months 14 days
Dividend yield	0.00%	0.00%
Volatility		46.67%
Hercules \| Warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of underlying stock per share	$ 1.99
Risk-free interest rate	1.96%
Expected term	6 years 10 months 6 days
Dividend yield	0.00%
Volatility	71.59%
Prior Note \| Warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of underlying stock per share	$ 0.31
Risk-free interest rate	1.04%
Dividend yield	0.00%
Volatility	90.78%
Conversion Feature
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of underlying stock per share	$ 0.31
Risk-free interest rate	1.04%
Dividend yield	0.00%
Volatility	86.91%
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Risk-free interest rate	1.81%
Expected term	8 years 3 months 14 days
Volatility	66.00%
Minimum \| Prior Note \| Warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected term	3 years 3 months 14 days
Minimum \| Conversion Feature
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected term	3 years 9 months 14 days
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Risk-free interest rate	2.24%
Expected term	10 years
Volatility	70.21%
Maximum \| Prior Note \| Warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected term	3 years 10 months 6 days
Maximum \| Conversion Feature
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected term	4 years 4 months 6 days

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).

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=25499696&loc=d3e19207-110258

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- Definition

Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

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

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- Definition

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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