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 $)	6 Months Ended
	Jun. 30, 2014	Jun. 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	3,364,033	3,574
Proceeds from stock issued for warrant and option exercises & ESPP purchases	$ 6,780,000	$ 2,000