Collaboration Agreements - Development and Commercialization Cost - Sharing Payments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Development cost-sharing payments [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development cost-sharing payments	$ 46,594	$ 49,213	$ 56,650
Development cost-sharing payments [Member] | Astellas Pharma Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development cost-sharing payments	46,594	47,473	44,285
Development cost-sharing payments [Member] | Pfizer [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development cost-sharing payments		1,740	12,365
Commercial cost sharing-payments [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Commercialization cost-sharing payments	(11,973)	(3,428)	(440)
Commercial cost sharing-payments [Member] | Astellas Pharma Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Commercialization cost-sharing payments	(11,973)	(3,437)	(472)
Commercial cost sharing-payments [Member] | Pfizer [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Commercialization cost-sharing payments		$ 9	$ 32