CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Net revenues from research collaborators	$ 66,725		$ 82,757		$ 100,041
Operating expenses:
Research and development	86,569	[1]	99,295	[1]	106,384	[1]
General and administrative	44,612	[1]	38,280	[1]	37,727	[1]
Restructuring of Tekmira license agreement	65,000
Total operating expenses	196,181		137,575		144,111
Loss from operations	(129,456)		(54,818)		(44,070)
Other income (expense):
Equity in loss of joint venture (Regulus Therapeutics Inc.)	(4,522)		(3,505)		(7,639)
Gain on issuance of stock by Regulus Therapeutics Inc.	16,084				4,421
Interest income	977		1,205		2,305
Other income (expense)	331		(531)		1,982
Total other income (expense)	12,870		(2,831)		1,069
Loss before income taxes	(116,586)		(57,649)		(43,001)
Benefit from (provision for) income taxes	10,572		0		(514)
Net loss	(106,014)		(57,649)		(43,515)
Net loss per common share - basic and diluted	$ (2.11)		$ (1.36)		$ (1.04)
Weighted average common shares used to compute basic and diluted net loss per common share	50,286		42,410		42,040
Comprehensive loss:
Net loss	(106,014)		(57,649)		(43,515)
Foreign currency translation					(29)
Unrealized gain (loss) on marketable securities, net of tax	15,827		(879)		27
Comprehensive loss	$ (90,187)		$ (58,528)		$ (43,517)

[1] Non-cash stock-based compensation expenses included in operating expenses are as follows: Research and development $ 8,041 $ 10,921 $ 11,689 General and administrative 4,319 5,755 7,429