CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue:
Research and development revenue under collaborative agreements	$ 325,898	$ 281,360	$ 202,514
Licensing and royalty revenue	20,722	2,343	11,647
Total revenue	346,620	283,703	214,161
Expenses:
Research, development and patent expenses	344,320	322,292	241,751
General and administrative	48,616	37,173	20,140
Total operating expenses	392,936	359,465	261,891
Income (loss) from operations	(46,316)	(75,762)	(47,730)
Other income (expense):
Investment income	5,416	4,302	2,682
Interest expense	(38,795)	(36,732)	(22,209)
Gain on investments, net	56	75	1,256
Gain on investment in Regulus Therapeutics Inc.	0	20,211	19,902
Loss on early retirement of debt	(3,983)	0	(8,292)
Loss before income tax (expense) benefit	(83,622)	(87,906)	(54,391)
Income tax (expense) benefit	(2,934)	(372)	15,407
Net loss	$ (86,556)	$ (88,278)	$ (38,984)
Basic and diluted net loss per share (in dollars per share)	$ (0.72)	$ (0.74)	$ (0.33)
Shares used in computing basic and diluted net loss per share (in shares)	120,933	119,719	117,691