Selected Quarterly Financial Data - Quarterly Financial Data (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
Income Statement [Abstract]
Product sales	$ 13,973	$ 7,240	$ 10,968	$ 7,974	$ 7,460	$ 6,096	$ 5,802	$ 5,795	$ 40,155	$ 25,152	$ 44,846
Total revenue	39,370	59,952	22,661	108,801	19,551	132,871	28,513	19,771	230,784	200,707	148,921
Cost of goods sold	8,364	6,760	10,534	8,444	6,298	9,220	5,108	7,907	34,102	28,533	38,509
Research and development expenses	47,135	43,229	45,412	47,011	38,494	34,200	36,702	38,338	182,787	147,734	190,010
Operating income (loss)	(29,364)	419	(43,469)	43,043	(37,488)	80,321	(22,916)	(36,402)	(29,371)	(16,485)	(120,130)
Net income (loss)	$ (54,137)	$ (8,203)	$ (52,657)	$ 33,820	$ (45,683)	$ 70,605	$ (32,637)	$ (46,201)	$ (81,177)	$ (53,916)	$ (162,013)
Net income (loss) per share
Basic	$ (0.40)	$ (0.06)	$ (0.40)	$ 0.26	$ (0.35)	$ 0.55	$ (0.26)	$ (0.37)
Diluted	$ (0.40)	$ (0.06)	$ (0.40)	$ 0.25	$ (0.35)	$ 0.53	$ (0.26)	$ (0.37)