Collaboration And License Agreements (Schedule Of Revenues Recognized Under The Agreements) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenue from collaboration and license agreements	$ 51,537	$ 107,470	$ 51,965
Millennium [Member]
Revenue from collaboration and license agreements	27,914	16,040	1,690
Genentech [Member]
Revenue from collaboration and license agreements	5,302	82,819	41,594
Pfizer [Member]
Revenue from collaboration and license agreements	4,500	0	0
Agensys [Member]
Revenue from collaboration and license agreements	3,957	2,256	4,029
Abbott [Member]
Revenue from collaboration and license agreements	3,721	219	0
GSK [Member]
Revenue from collaboration and license agreements	3,037	3,013	0
Other [Member]
Revenue from collaboration and license agreements	$ 3,106	$ 3,123	$ 4,652