Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenue:
Collaboration revenue	$ 1,499	$ 6,344
Total revenue	1,499	6,344
Operating expenses:
Research and development	41,911	23,719
General and administrative	15,955	7,336
Change in fair value of contingent consideration	1,013	215
Total operating expenses	58,879	31,270
Loss from operations	(57,380)	(24,926)
Other income, net	961	139
Loss before income taxes	(56,419)	(24,787)
Income tax benefit	145
Net loss	$ (56,274)	$ (24,787)
Net loss per share - basic and diluted:	$ (1.52)	$ (0.76)
Weighted-average number of common shares used in computing net loss per share - basic and diluted:	36,920	32,558
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net of tax of $0.7 million for the three months ended March 31, 2016	$ 1,319	$ (52)
Comprehensive loss	$ (54,955)	$ (24,839)