Financing - Additional Information 1 (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended
	Feb. 10, 2014	Sep. 30, 2013	May 07, 2013	Feb. 10, 2014	Sep. 30, 2013
Class of Stock [Line Items]
Common stock sold		13,727,251
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 40.1	$ 27.7	$ 16.5
Price to the public per share of common stock		$ 1.55
Sales price per share of prefunded warrants				$ 3.99	$ 1.54
Estimated net proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 37.2	$ 25.7
Common Stock [Member]
Class of Stock [Line Items]
Common stock sold	7,867,438
Price to the public per share of common stock	$ 4.00
Pre-funded warrants [Member]
Class of Stock [Line Items]
Shares of common stock that may be purchased upon exercise of the warrants			15,816,327	2,158,750	4,175,975
Warrant exercise price (per share)			$ 0.01	$ 0.01	$ 0.01
Pre-funded warrants expiration date	Feb. 10, 2021	Sep. 30, 2020