Selected Quarterly Results (Unaudited) - Selected Quarterly Results (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Information [Abstract]
Revenue	$ 12,510	$ 11,253	$ 8,744	$ 29,478	$ 3,931	$ 3,571	$ 5,004	$ 3,040	$ 32,209	$ 1,235	$ 1,733	$ 13,054	$ 61,985	$ 15,546	$ 48,231
Gross profit	7,275	6,808	4,573	23,833	1,631	1,257	910	490	29,552	(464)	(888)	11,930
Income (loss) from operations	(14,291)	(10,045)	(12,987)	7,903	(15,200)	(15,199)	(15,594)	(17,942)	10,954	(19,652)	(18,681)	(7,800)	(29,420)	(63,935)	(35,179)
Net income (loss)	$ (16,210)	$ (11,951)	$ (14,879)	$ 48,325	$ (15,942)	$ (15,977)	$ (16,486)	$ (18,733)	$ 10,171	$ (20,439)	$ (19,211)	$ (8,193)	$ 5,285	$ (67,138)	$ (37,672)
Basic income (loss) per share	$ (0.31)	$ (0.21)	$ (0.27)	$ 0.89	$ (0.29)	$ (0.30)	$ (0.31)	$ (0.35)	$ 0.20	$ (0.39)	$ (0.37)	$ (0.16)	$ 0.10	$ (1.25)	$ (0.72)
Diluted income (loss) per share	$ (0.30)	$ (0.21)	$ (0.27)	$ 0.87	$ (0.29)	$ (0.30)	$ (0.31)	$ (0.35)	$ 0.20	$ (0.39)	$ (0.37)	$ (0.16)	$ 0.09	$ (1.25)	$ (0.72)