Investment in Regulus Therapeutics Inc. (Details) (USD $)				1 Months Ended		12 Months Ended	1 Months Ended			1 Months Ended			12 Months Ended	1 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Regulus	Oct. 31, 2010 Collaborations Regulus	Jul. 31, 2010 Collaborations Regulus	Dec. 31, 2011 Collaborations Regulus	Oct. 31, 2010 Collaborations Sanofi Regulus	Jun. 30, 2010 Collaborations Sanofi Regulus Y	Dec. 31, 2011 Collaborations Sanofi Regulus	Oct. 31, 2010 Collaborations Sanofi Regulus Less than	Apr. 30, 2009 Collaborations Alnylam	Sep. 30, 2007 Collaborations Alnylam Regulus	Dec. 31, 2011 Collaborations Alnylam Regulus	May 31, 2011 Collaborations GlaxoSmithKline	Apr. 30, 2008 Collaborations GlaxoSmithKline Regulus instrument	Dec. 31, 2009 Collaborations GlaxoSmithKline Regulus
Regulus Collaborations
Equity investments							$ 10,000,000					$ 10,000,000
Equity ownership (as a percent)										10.00%
Equity ownership after other investments (as a percent)				46.00%
Potentially valued	(4,424,000)	(870,000)	(4,400,000)
Upfront fee					1,900,000			25,000,000			11,000,000			35,000,000	28,000,000
Number of years for which annual research support is provided								3
Number of years for which annual research support may be extended								2
Option period (in years)								3
Additional potential future payments under a collaborative arrangement option									50,000,000
Percentage of upfront payment and potential milestone payments to be received					7.50%	7.50%							7.50%
Option fees received															18,000,000
Number of note instruments received															2
Amount of notes receivable															5,000,000
Revenue recognized																3,000,000
Development, regulatory and sales milestone aggregate potential payments								$ 750,000,000