Common Stock Warrant and Option Exercises and Employee Stock Purchases - Additional Information (Detail) (Common Stock Warrant And Option Exercises And Employee Stock Purchases [Member], USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Common Stock Warrant And Option Exercises And Employee Stock Purchases [Member]
Employee Stock Option And Warrant Exercises And ESPP Purchases [Line Items]
Number of shares of common stock issued for stock warrant and stock options exercised and ESPP purchases	5,398,609	3,780,945
Proceeds from stock issued for warrant and option exercises & ESPP purchases	$ 8,132,000	$ 1,864,000