Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue:
Collaboration revenue	$ 4,940	$ 6,250	$ 11,284	$ 12,500
Research and license fees		85		170
Total revenue	4,940	6,335	11,284	12,670
Operating expenses:
Research and development	44,266	13,931	67,985	25,394
General and administrative	10,724	5,738	18,060	11,277
Change in fair value of contingent consideration	1,973		2,188
Total operating expenses	56,963	19,669	88,233	36,671
Loss from operations	(52,023)	(13,334)	(76,949)	(24,001)
Other income, net	228	11	367	69
Loss before income taxes	(51,795)	(13,323)	(76,582)	(23,932)
Benefit from income taxes		11,797		11,797
Net loss	(51,795)	(1,526)	(76,582)	(12,135)
Other comprehensive loss:
Unrealized gain on available-for-sale securities, net of tax	70		18
Comprehensive loss	$ (51,725)	$ (1,526)	$ (76,564)	$ (12,135)
Net loss per share - basic and diluted:	$ (1.57)	$ (0.06)	$ (2.34)	$ (0.50)
Weighted-average number of common shares used in computing net loss per share - basic and diluted:	32,955	24,474	32,757	24,312