Financing - Additional Information 1 (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended
	Feb. 10, 2014	May 07, 2013	Feb. 10, 2014
Equity [Line Items]
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 40.1	$ 16.5
Sales price per share of prefunded warrants			$ 3.99
Estimated net proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 37.2
Common Stock [Member]
Equity [Line Items]
Common stock sold	7,867,438
Price to the public per share of common stock	$ 4.00
Pre-funded warrants [Member]
Equity [Line Items]
Shares of common stock that may be purchased upon exercise of the warrants		15,816,327	2,158,750
Warrants exercise price per share		0.01	0.01
Pre-funded warrants expiration date	Feb. 10, 2021