Collaboration Agreements (Schedule Of Collaboration Revenue Attributable To Up-Front And Milestone Payments) (Detail) (Up-Front Cash Payment Arrangement [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total	$ 145,944	$ 60,389	$ 62,508
Astellas [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total	73,914	24,374	23,492
Pfizer [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total	$ 72,030	$ 36,015	$ 39,016