Fair Value of Warrants Using Valuation Model (Detail)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
2009 Warrants
Class of Warrant or Right [Line Items]
Expected term (in years)	1 year 7 months 24 days	2 years 7 months 24 days
Estimated volatility	45.00%	74.00%
Risk-free interest rate	0.25%	0.36%
Expected dividend yield	0.00%	0.00%
2010 Warrants
Class of Warrant or Right [Line Items]
Expected term (in years)	2 years 10 months 10 days	3 years 10 months 10 days
Estimated volatility	51.00%	70.00%
Risk-free interest rate	0.36%	0.60%
Expected dividend yield	0.00%	0.00%

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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=7578670&loc=d3e19207-110258

+ Details

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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

+ Details

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- Definition

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

+ References

+ Details

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- Definition

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

+ References

+ Details

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