Fair Value of Financial Instruments - Additional Information (Detail)	3 Months Ended	6 Months Ended	9 Months Ended
	Mar. 31, 2013	Jun. 30, 2013	Sep. 30, 2013
2010 Warrants [Member]
Class of Stock [Line Items]
Weighted average term	2 years	1 year 8 months 12 days	1 year 6 months
Warrant exercise price probability	5.00%	5.00%	5.00%
Risk free interest rate	0.25%	0.36%	0.33%
2010 Warrants [Member] | Maximum [Member]
Class of Stock [Line Items]
Percentage of volatility	59.10%	56.50%	59.40%
2010 Warrants [Member] | Minimum [Member]
Class of Stock [Line Items]
Percentage of volatility	58.00%	55.70%	59.00%
2011 Warrants [Member]
Class of Stock [Line Items]
Weighted average term	2 years 9 months 18 days	2 years 6 months	2 years 3 months 18 days
Warrant exercise price probability	5.00%	5.00%	5.00%
2011 Warrants [Member] | Maximum [Member]
Class of Stock [Line Items]
Risk free interest rate	0.25%	0.66%	0.63%
Percentage of volatility	59.10%	59.10%	58.60%
2011 Warrants [Member] | Minimum [Member]
Class of Stock [Line Items]
Risk free interest rate			0.33%
Percentage of volatility	58.00%
2013 Warrants [Member]
Class of Stock [Line Items]
Weighted average term	4 years 10 months 24 days	4 years 8 months 12 days	4 years 4 months 24 days
Warrant exercise price probability	5.00%	5.00%	5.00%
2013 Warrants [Member] | Maximum [Member]
Class of Stock [Line Items]
Risk free interest rate	0.77%	1.41%	1.39%
Percentage of volatility	66.70%	64.60%	64.30%
2013 Warrants [Member] | Minimum [Member]
Class of Stock [Line Items]
Risk free interest rate	0.25%
Percentage of volatility	58.00%