CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenue:
Research and development revenue under collaborative agreements	$ 23,383	$ 11,127	$ 102,918	$ 80,085
Licensing and royalty revenue	202	474	2,118	2,091
Total revenue	23,585	11,601	105,036	82,176
Expenses:
Research, development and patent expenses	45,660	36,551	126,603	115,700
General and administrative	3,430	3,096	10,241	9,281
Total operating expenses	49,090	39,647	136,844	124,981
Loss from operations	(25,505)	(28,046)	(31,808)	(42,805)
Other income (expense):
Equity in net loss of Regulus Therapeutics Inc.				(1,139)
Investment income	434	408	1,400	1,485
Interest expense	(4,867)	(5,937)	(14,470)	(16,335)
Gain on investments, net	175		2,073	19
Loss on early retirement of debt		(4,770)		(4,770)
Loss before income tax benefit	(29,763)	(38,345)	(42,805)	(63,545)
Income tax benefit	5,193	706	6,437	704
Net loss	$ (24,570)	$ (37,639)	$ (36,368)	$ (62,841)
Basic and diluted net loss per share (in dollars per share)	$ (0.21)	$ (0.37)	$ (0.33)	$ (0.63)
Shares used in computing basic net loss per share (in shares)	115,263	100,680	108,608	100,351
Shares used in computing diluted net loss per share (in shares)	115,263	100,680	108,608	100,351