Black-Scholes Option Pricing Model Assumptions to Estimate Fair Value of Warrants (Detail)	0 Months Ended	1 Months Ended	12 Months Ended
Dec. 03, 2007	Dec. 31, 2010	Aug. 21, 2007	Dec. 31, 2012	Dec. 31, 2012 August and December 2007 Warrants	Dec. 31, 2011 August and December 2007 Warrants	Dec. 31, 2012 January 2011 Warrants	Dec. 31, 2011 January 2011 Warrants
Class of Warrant or Right [Line Items]
Annual dividend yield	0.00%	0.00%	0.00%	0.00%		0.00%	0.00%	0.00%
Expected life (years)	4 years 8 months 19 days	3 years		5 years	0 years	1 year	3 years 18 days	4 years 18 days
Risk-free interest rate	3.28%	1.10%	4.05%	4.94%		0.12%	0.72%	0.83%
Expected volatility	122.90%	112.60%	118.00%	113.00%		95.00%	117.00%	109.00%

Name:	us-gaap_ClassOfWarrantOrRightLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

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

Name:	us-gaap_FairValueAssumptionsExpectedDividendRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	us-gaap_FairValueAssumptionsExpectedTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsExpectedVolatilityRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsRiskFreeInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration