CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenue:
Research and development revenue under collaborative agreements	$ 20,189	$ 27,785	$ 64,508	$ 77,484
Licensing and royalty revenue	524	839	2,175	4,569
Total revenue	20,713	28,624	66,683	82,053
Expenses:
Research and development	39,924	34,716	110,178	105,827
General and administrative	3,105	2,855	8,989	8,724
Total operating expenses	43,029	37,571	119,167	114,551
Loss from operations	(22,316)	(8,947)	(52,484)	(32,498)
Other income (expense):
Equity in net loss of Regulus Therapeutics Inc.	(386)	(930)	(2,275)	(6,358)
Investment income	575	776	1,896	2,590
Interest expense	(4,773)	(3,338)	(11,624)	(9,835)
Gain (loss) on investments, net	18	(15)	(267)	(1,162)
Loss before income tax expense	(26,882)	(12,454)	(64,754)	(47,263)
Income tax expense			(11)	(2)
Net loss	$ (26,882)	$ (12,454)	$ (64,765)	$ (47,265)
Basic net loss per share (in dollars per share)	$ (0.27)	$ (0.13)	$ (0.65)	$ (0.48)
Diluted net loss per share (in dollars per share)	$ (0.27)	$ (0.13)	$ (0.65)	$ (0.48)
Shares used in computing basic net loss per share (in shares)	99,687	99,196	99,620	99,101
Shares used in computing diluted net loss per share (in shares)	99,687	99,196	99,620	99,101