Collaboration Agreements (Schedule Of Collaboration Revenue) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Collaboration revenue	$ 42,912	$ 15,799	$ 79,737	$ 30,508
Astellas [Member]
Collaboration revenue	7,256	6,795	13,193	12,500
Pfizer [Member]
Collaboration revenue	$ 35,656	$ 9,004	$ 66,544	$ 18,008