Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Selected Quarterly Financial Data (Unaudited)
Product revenue	$ 17,810	$ 8,666	$ 19,305	$ 2,722	$ 4,747	$ 4,714	$ 5,690	$ 4,812	$ 48,503	$ 19,963	$ 16,701
Research and development revenue	4,583	5,129	25,595	5,840	16,432	4,622	5,260	5,973
Total collaboration revenue	22,393	13,795	44,900	8,562	21,179	9,336	10,950	10,785	89,650	52,250	35,465
Net loss	(29,164)	(30,050)	(2,222)	(21,877)	(15,981)	(29,101)	(26,156)	(27,362)	(83,313)	(98,600)	(108,408)
Comprehensive loss	$ (29,176)	$ (30,054)	$ (2,204)	$ (21,859)	$ (16,017)	$ (29,127)	$ (26,119)	$ (27,378)	$ (83,293)	$ (98,641)	$ (108,494)
Basic and diluted net loss per common share	$ (0.43)	$ (0.44)	$ (0.04)	$ (0.40)	$ (0.31)	$ (0.56)	$ (0.51)	$ (0.53)	$ (1.32)	$ (1.91)	$ (2.13)
Weighted average shares used in computing basic and diluted net loss per share (in shares)	68,138	68,004	61,680	54,492	52,255	51,545	51,466	51,356	63,130	51,664	50,907