Financings - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2013	May 07, 2013	Sep. 30, 2013	Sep. 30, 2013
Equity [Line Items]
Common stock sold	13,727,251	17,500,000
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 27,700,000	$ 16,500,000
Common Stock price per share	$ 1.55		$ 1.55	$ 1.55
Estimated net proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	25,600,000	14,600,000
Issuance of warrants to purchase common stock		17,500,000
Redemption price per share of warrants		0.01
Notice period to holder prior to redemption of warrants by Company		30 days
Minimum trading days considered to redeem warrants		20 days
Minimum closing price to redeem the warrants		2.80
Proceeds from exercise of warrants			$ 1,713,000	$ 1,713,000
Exercise price of warrants exercised during the period			$ 0.47	$ 0.47
Shares issued on exercise of warrants during the period			3,645,000	3,645,000
Pre-funded Warrants [Member]
Equity [Line Items]
Shares of common stock that may be purchased upon exercise of the warrants	4,175,975	15,816,327	4,175,975	4,175,975
Prefunded Warrants Exercise price per share	0.01	0.01	0.01	0.01
Sales price per share of prefunded warrants	$ 1.54		$ 1.54	$ 1.54
Pre-funded warrants Expiration Date	Sep. 30, 2020
Matching Warrants Two [Member]
Equity [Line Items]
Shares of common stock that may be purchased upon exercise of the warrants		15,816,327