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	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Apr. 04, 2012 Securities Purchase Agreement [Member]	Jun. 30, 2013 Securities Purchase Agreement [Member]	Mar. 31, 2013 Securities Purchase Agreement [Member]	Dec. 31, 2012 Securities Purchase Agreement [Member]	Sep. 30, 2012 Securities Purchase Agreement [Member]	Jun. 30, 2012 Securities Purchase Agreement [Member]	Jun. 05, 2012 Loan and Security Agreement [Member]	Jun. 30, 2013 Loan and Security Agreement [Member]	Mar. 31, 2013 Loan and Security Agreement [Member]	Dec. 31, 2012 Loan and Security Agreement [Member]	Sep. 30, 2012 Loan and Security Agreement [Member]	Jun. 30, 2012 Loan and Security Agreement [Member]
Derivative [Line Items]
Risk-free interest rate	0.44%	0.21%	0.20%	0.23%	0.23%	0.33%	1.19%	1.13%	0.67%	0.75%	0.63%	0.77%	0.77%	1.20%	0.70%	0.75%	0.64%	0.80%
Expected annual dividend yield	15.00%	16.70%	16.50%	16.50%	15.00%	16.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
Expected volatility	75.00%	65.80%	66.90%	73.50%	70.00%	71.00%	80.00%	71.90%	71.70%	80.60%	80.90%	80.80%	79.99%	72.30%	72.01%	80.14%	81.18%	80.32%
Term (years)	2 years 6 months	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 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 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	$ 3.0	$ 3.4	$ 4.4	$ 7.1	$ 8.6	$ 0.4	$ 0.2	$ 0.2	$ 0.2	$ 0.4	$ 0.5

Warrant instruments, fair value disclosure.

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

+ References

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

+ References

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