Financing - May 2013 Follow-on Underwritten Public Offering (Detail) (USD $)	0 Months Ended
	May 07, 2013	Feb. 10, 2014	May 07, 2013
Common Stock [Member]
Equity [Line Items]
Number of shares of common stock sold in financing	17,500,000
Common Stock and Matching Warrants Sold [Member]
Equity [Line Items]
Combined price to the public per share of common stock	$ 0.50		$ 0.50
Common Stock and Matching Warrants Sold [Member] | Common Stock [Member]
Equity [Line Items]
Number of shares of common stock sold in financing	17,500,000
Pre-funded Warrants & Matching Warrants Sold [Member]
Equity [Line Items]
Combined price to the public per share of common stock	$ 0.49		$ 0.49
Matching Warrants [Member]
Equity [Line Items]
Total (shares)			33,316,327
Warrant exercise price (per share)			0.47
Term of warrant (years)	5 years
Matching Warrants [Member] | Common Stock and Matching Warrants Sold [Member]
Equity [Line Items]
Total (shares)	17,500,000		17,500,000
Matching Warrants [Member] | Pre-funded Warrants & Matching Warrants Sold [Member]
Equity [Line Items]
Total (shares)	15,816,327		15,816,327
Pre-funded warrants [Member]
Equity [Line Items]
Total (shares)		2,158,750	15,816,327
Warrant exercise price (per share)		0.01	0.01
Term of warrant (years)	7 years
Pre-funded warrants [Member] | Pre-funded Warrants & Matching Warrants Sold [Member]
Equity [Line Items]
Total (shares)	15,816,327		15,816,327