Collaboration Agreements (Development And Commercialization Cost-Sharing Payments Receivable) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Development Milestone Payments [Member]
Collaboration Agreements [Line Items]
Development cost-sharing payments	$ 15,442	$ 14,802
Commercial Milestone Payments [Member]
Collaboration Agreements [Line Items]
Commercialization cost-sharing payments	(812)	(55)
Astellas [Member] | Development Milestone Payments [Member]
Collaboration Agreements [Line Items]
Development cost-sharing payments	14,115	9,887
Astellas [Member] | Commercial Milestone Payments [Member]
Collaboration Agreements [Line Items]
Commercialization cost-sharing payments	(816)	(68)
Pfizer [Member] | Development Milestone Payments [Member]
Collaboration Agreements [Line Items]
Development cost-sharing payments	1,327	4,915
Pfizer [Member] | Commercial Milestone Payments [Member]
Collaboration Agreements [Line Items]
Commercialization cost-sharing payments	$ 4	$ 13