CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue:
Research and development revenue under collaborative agreements	$ 144,194	$ 96,415	$ 96,190
Licensing and royalty revenue	3,091	5,634	2,896
Total revenue	147,285	102,049	99,086
Expenses:
Research, development and patent expenses	184,033	158,458	157,397
General and administrative	14,918	12,515	12,789
Total operating expenses	198,951	170,973	170,186
Loss from operations	(51,666)	(68,924)	(71,100)
Other income (expense):
Equity in net loss of Regulus Therapeutics Inc.		(1,406)	(3,554)
Investment income	2,085	1,844	2,414
Interest expense	(19,355)	(21,152)	(16,732)
Gain on investments, net	2,378	1,465	4,182
Gain on investment in Regulus Therapeutics Inc.		18,356
Loss on early retirement of debt		(4,770)
Loss before income tax benefit (expense)	(66,558)	(74,587)	(84,790)
Income tax benefit (expense)	5,914	9,109	(11)
Net loss	$ (60,644)	$ (65,478)	$ (84,801)
Basic and diluted net loss per share (in dollars per share)	$ (0.55)	$ (0.65)	$ (0.85)
Shares used in computing basic net loss per share (in shares)	110,502	100,576	99,656
Shares used in computing diluted net loss per share (in shares)	110,502	100,576	99,656