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Warrants and Derivative Liabilities - Schedule of Fair Value of Warrants Using Black-Scholes Option Pricing Model (Detail) (USD $) In Millions, unless otherwise specified | 0 Months Ended | 3 Months Ended | 0 Months Ended | 3 Months Ended | 0 Months Ended | 3 Months Ended
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Apr. 04, 2012 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Apr. 04, 2012 Securities Purchase Agreement | Sep. 30, 2013 Securities Purchase Agreement | Jun. 30, 2013 Securities Purchase Agreement | Mar. 31, 2013 Securities Purchase Agreement | Dec. 31, 2012 Securities Purchase Agreement | Sep. 30, 2012 Securities Purchase Agreement | Jun. 30, 2012 Securities Purchase Agreement | Jun. 05, 2012 Loan and Security Agreement | Sep. 30, 2013 Loan and Security Agreement | Jun. 30, 2013 Loan and Security Agreement | Mar. 31, 2013 Loan and Security Agreement | Dec. 31, 2012 Loan and Security Agreement | Sep. 30, 2012 Loan and Security Agreement | Jun. 30, 2012 Loan and Security Agreement
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk-free interest rate | 0.44% | 1.00% | 0.21% | 0.20% | 0.23% | 0.23% | 0.33% | 1.19% | 1.02% | 1.13% | 0.67% | 0.75% | 0.63% | 0.77% | 0.77% | 1.09% | 1.20% | 0.70% | 0.75% | 0.64% | 0.80%
Expected annual dividend yield | 15.00% | 15.50% | 16.70% | 16.50% | 16.50% | 15.00% | 16.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expected volatility | 75.00% | 66.30% | 65.80% | 66.90% | 73.50% | 70.00% | 71.00% | 80.00% | 72.00% | 71.90% | 71.70% | 80.60% | 80.90% | 80.80% | 79.99% | 72.10% | 72.30% | 72.01% | 80.14% | 81.18% | 80.32%
Term (years) | 2 years 6 months | 1 year | 1 year 3 months 4 days | 1 year 6 months 4 days | 1 year 9 months 4 days | 2 years 4 days | 2 years 3 months 11 days | 5 years 6 months | 4 years 4 days | 4 years 3 months 7 days | 4 years 6 months 4 days | 4 years 9 months 4 days | 5 years 4 days | 5 years 3 months 11 days | 5 years 6 months | 4 years 2 months 5 days | 4 years 5 months 5 days | 4 years 8 months 5 days | 4 years 11 months 5 days | 5 years 2 months 5 days | 5 years 5 months 9 days
Fair value |  |  |  |  |  |  |  | $ 7.0 | $ 2.5 | $ 3.0 | $ 3.4 | $ 4.4 | $ 7.1 | $ 8.6 | $ 0.4 | $ 0.2 | $ 0.2 | $ 0.2 | $ 0.2 | $ 0.4 | $ 0.5

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- Definition Warrant instruments, fair value disclosure. + References No definition available. + Details
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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=25499696&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 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 + 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 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 + Details
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- Definition Risk-free interest rate assumption used in valuing an instrument. + 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=25499696&loc=d3e19207-110258 + Details
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