Quarterly Results of Operation (Unaudited) - Summary of Unaudited Quarterly Results of Operations (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]
Total revenues					$ 134	$ 61	$ 113	$ 93		$ 401	$ 1,431
Cost of goods sold					435	202	238	220		1,095	4,810
Amortization of intangible assets	$ 1,596	$ 338	$ 126	$ 125	126	125	126	126	$ 2,185	503	500
Acquisition related costs	228	4,003							4,231
Other operating expenses	12,076	9,223	8,942	9,714	7,373	11,004	10,130	6,905	39,955	35,412
Interest expense, net	604	436	280	281	279	237	206	321	1,601	1,043	954
Loss before income taxes	(14,504)	(14,000)	(9,348)	(10,120)	(8,079)	(11,507)	(10,587)	(7,479)	(47,972)	(37,652)	(28,358)
Income tax benefit	925	99							1,024
Net loss	$ (13,579)	$ (13,901)	$ (9,348)	$ (10,120)	$ (8,079)	$ (11,507)	$ (10,587)	$ (7,479)	$ (46,948)	$ (37,652)	$ (28,358)
Net loss per share - basic and diluted	$ (0.13)	$ (0.16)	$ (0.14)	$ (0.16)	$ (0.13)	$ (0.18)	$ (0.18)	$ (0.15)	$ (0.59)	$ (0.64)	$ (2.23)