Financing - Additional Information 3 (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended
	Feb. 10, 2014	Sep. 30, 2013	May 07, 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
Pre-funded warrants [Member]
Class of Stock [Line Items]
Issuance of warrants to purchase shares common stock			15,816,327
Common Stock [Member]
Class of Stock [Line Items]
Common stock sold			17,500,000
Matching Warrants [Member] | Pre-funded warrants [Member]
Class of Stock [Line Items]
Issuance of warrants to purchase shares common stock			15,816,327
Matching Warrants [Member] | Common Stock [Member]
Class of Stock [Line Items]
Issuance of warrants to purchase shares common stock			17,500,000