Warrants and Derivative Liabilities - Schedule of Assumptions Used to Calculate the Fair Value of Warrants (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended											0 Months Ended		3 Months Ended							0 Months Ended			3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2014 Senior Convertible Note Warrant	Jun. 30, 2014 Senior Convertible Note Warrant	Mar. 31, 2014 Senior Convertible Note Warrant	Dec. 31, 2013 Senior Convertible Note Warrant	Sep. 30, 2013 Senior Convertible Note Warrant	Jun. 30, 2013 Senior Convertible Note Warrant	Mar. 31, 2013 Senior Convertible Note Warrant	Oct. 09, 2013 Senior Convertible Note Warrant Post Modification	Oct. 09, 2013 Senior Convertible Note Warrant Pre Modification	Sep. 30, 2014 Senior Secured Term Loan First Warrant	Jun. 30, 2014 Senior Secured Term Loan First Warrant	Mar. 31, 2014 Senior Secured Term Loan First Warrant	Dec. 31, 2013 Senior Secured Term Loan First Warrant	Sep. 30, 2013 Senior Secured Term Loan First Warrant	Jun. 30, 2013 Senior Secured Term Loan First Warrant	Mar. 31, 2013 Senior Secured Term Loan First Warrant	Nov. 15, 2013 Senior Secured Term Loan First Warrant Post Modification	Nov. 15, 2013 Senior Secured Term Loan First Warrant Pre Modification	Nov. 15, 2013 Senior Secured Term Loan Second Warrant	Sep. 30, 2014 Senior Secured Term Loan Second Warrant	Jun. 30, 2014 Senior Secured Term Loan Second Warrant	Mar. 31, 2014 Senior Secured Term Loan Second Warrant	Dec. 31, 2013 Senior Secured Term Loan Second Warrant
Derivative [Line Items]
Risk-free interest rate	0.12%	0.10%	0.21%	0.20%	1.07%	0.98%	1.11%	1.17%	1.02%	1.13%	0.67%	1.05%	1.05%	1.13%	1.04%	1.18%	1.24%	1.09%	1.20%	0.70%	1.00%	1.00%	1.55%	1.65%	1.57%	1.76%	1.89%
Expected annual dividend yield	16.50%	15.50%	16.70%	16.50%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
Expected volatility	68.63%	66.26%	65.80%	66.91%	76.20%	83.50%	80.99%	75.60%	71.98%	71.90%	71.74%	71.45%	71.45%	78.30%	82.75%	80.73%	74.79%	72.10%	72.30%	72.01%	72.64%	72.64%	76.97%	78.10%	80.00%	79.73%	80.37%
Term (years)	9 months	1 year	1 year 3 months 4 days	1 year 6 months 4 days	3 years 4 days	3 years 3 months 4 days	3 years 6 months 4 days	3 years 9 months 4 days	4 years 4 days	4 years 3 months 7 days	4 years 6 months 4 days	3 years 11 months 27 days	3 years 11 months 27 days	3 years 2 months 5 days	3 years 5 months 5 days	3 years 8 months 5 days	3 years 11 months 5 days	4 years 2 months 5 days	4 years 5 months 5 days	4 years 8 months 5 days	4 years 18 days	4 years 18 days	5 years 5 months 27 days	4 years 7 months 13 days	4 years 10 months 13 days	5 years 1 month 13 days	5 years 4 months 13 days
Fair value					$ 1.5	$ 2.3	$ 2.2	$ 2.2	$ 2.5	$ 3.0	$ 3.4	$ 3.2	$ 2.2	$ 0.1	$ 0.1	$ 0.1	$ 0.1	$ 0.2	$ 0.2	$ 0.2	$ 0.1	$ 0.1	$ 0.3	$ 0.2	$ 0.3	$ 0.3	$ 0.3