CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenue:
Research and development revenue under collaborative agreements	$ 47,140	$ 24,305	$ 68,957	$ 44,319
Licensing and royalty revenue	200	518	1,618	1,651
Total revenue	47,340	24,823	70,575	45,970
Expenses:
Research and development	40,435	36,009	79,149	70,254
General and administrative	3,209	2,874	6,185	5,884
Total operating expenses	43,644	38,883	85,334	76,138
Income (loss) from operations	3,696	(14,060)	(14,759)	(30,168)
Other income (expense):
Equity in net loss of Regulus Therapeutics Inc.	(163)	(1,033)	(1,139)	(1,889)
Investment income	477	616	1,077	1,321
Interest expense	(5,219)	(3,437)	(10,398)	(6,851)
Gain (loss) on investments, net	2	34	19	(285)
Loss before income tax expense	(1,207)	(17,880)	(25,200)	(37,872)
Income tax expense		(9)	(2)	(11)
Net loss	$ (1,207)	$ (17,889)	$ (25,202)	$ (37,883)
Basic and diluted net loss per share (in dollars per share)	$ (0.01)	$ (0.18)	$ (0.25)	$ (0.38)
Shares used in computing basic net loss per share (in shares)	100,213	99,602	100,185	99,586
Shares used in computing diluted net loss per share (in shares)	100,213	99,602	100,185	99,586