Summarized Quarterly Financial Data (Unaudited) - Schedule of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Net revenue	$ 187	$ 130	$ 88	$ 6					$ 411
Gross profit (loss)	(567)	72	33	(19)					(481)
Operating loss	(4,196)	(4,668)	(4,564)	(4,668)	$ (3,301)	$ (2,120)	$ (1,539)	$ (2,345)	(18,096)	$ (9,305)	$ (7,604)
Net income (loss)	$ (10,127)	$ (4,422)	$ 7,136	$ (32,968)	$ 420	$ (14,373)	$ (8,069)	$ (3,358)	$ (40,381)	$ (25,380)	$ (20,939)
Net income (loss) per share, basic	$ (0.18)	$ (0.07)	$ 0.12	$ (0.54)	$ 0.01	$ (0.24)	$ (0.13)	$ (0.06)
Net income (loss) per share, diluted	$ (0.18)	$ (0.07)	$ (0.04)	$ (0.54)	$ 0.01	$ (0.24)	$ (0.13)	$ (0.06)