Commitments and Contingencies, Research Collaboration and Licensing Agreements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended			1 Months Ended
	Dec. 31, 2011 Agreements with Royalty Provisions [Member] Percent	Dec. 31, 2010 Agreements with Royalty Provisions [Member]	Dec. 31, 2009 Agreements with Royalty Provisions [Member]	Jul. 31, 2008 Cellectis Agreement [Member]	Dec. 31, 2011 Cellectis Agreement [Member]	Dec. 31, 2010 Cellectis Agreement [Member]	Dec. 31, 2009 Cellectis Agreement [Member]	Dec. 31, 2011 License Agreement With Genentech [Member] Percent
Research collaboration and licensing agreements [Abstract]
Royalty rate, minimum (in hundredths)	0.25%
Royalty rate, maximum (in hundredths)	16.50%
Royalty expense	$ 3.2	$ 1.7	$ 1.5
Non-refundable advance payment made under license agreement				12.5
Amortization of advance payment					1.0	0.9	2.3
Unamortized balance of advance payment					5.7	6.6
Future amortization expense of advance payment [Abstract]
2012					1.0
2013					1.0
2014					0.9
2015					0.9
2016					0.9
Amount of payment to be made upon reaching minimum sales target								60
Cumulative sales range, minimum								400
Royalty payment percentage of cumulative sales within cumulative sales range (in hundredths)								4.75%
Cumulative sales range, maximum								$ 3,000
Royalty payment percentage of cumulative sales over range (in hundredths)								5.50%