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
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

Warrant instruments, fair value disclosure.

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- 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

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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.

+ References

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- Definition

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

+ References

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