Collaboration Agreements (Development And Commercialization Cost-Sharing Payments) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Development Cost-Sharing Payments [Member]
Collaboration Agreements [Line Items]
Development cost-sharing payments	$ 49,213	$ 56,650	$ 63,264
Development Cost-Sharing Payments [Member] | Astellas [Member]
Collaboration Agreements [Line Items]
Development cost-sharing payments	47,473	44,285	34,125
Development Cost-Sharing Payments [Member] | Pfizer [Member]
Collaboration Agreements [Line Items]
Development cost-sharing payments	1,740	12,365	29,139
Commercial Cost Sharing Payments [Member]
Collaboration Agreements [Line Items]
Commercialization cost-sharing payments	(3,428)	(440)	(564)
Commercial Cost Sharing Payments [Member] | Astellas [Member]
Collaboration Agreements [Line Items]
Commercialization cost-sharing payments	(3,437)	(472)	520
Commercial Cost Sharing Payments [Member] | Pfizer [Member]
Collaboration Agreements [Line Items]
Commercialization cost-sharing payments	$ 9	$ 32	$ (1,084)