License and Collaboration Agreements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified								1 Months Ended	2 Months Ended	3 Months Ended					1 Months Ended	3 Months Ended	12 Months Ended	1 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Naloxegol [Member]	Mar. 31, 2013 AstraZeneca AB [Member]	Mar. 31, 2013 AstraZeneca AB [Member] Naloxegol [Member]	Mar. 31, 2013 AstraZeneca AB [Member] Naloxegol fixed-dose combination programs [Member]	Mar. 31, 2013 Roche [Member] PEGASYS [Member]	Mar. 31, 2013 Roche [Member] MIRCERA [Member]	Feb. 29, 2012 Roche [Member] MIRCERA [Member] Performance-based milestone payments [Member]	Feb. 29, 2012 Roche [Member] MIRCERA [Member] Upfront payment arrangement [Member]	Mar. 31, 2013 Roche [Member] MIRCERA [Member] Upfront payment arrangement [Member] Performance-based milestone payments [Member]	Mar. 31, 2013 Amgen, Inc. [Member]	Mar. 31, 2013 Baxter Healthcare [Member] Hemophilia [Member]	Mar. 31, 2013 Affymax, Inc. [Member] Omontys [Member]	Mar. 31, 2013 Other [Member]	Apr. 30, 2013 Bayer Healthcare LLC [Member]	Mar. 31, 2013 Bayer Healthcare LLC [Member]	Dec. 31, 2012 Bayer Healthcare LLC [Member]	Dec. 31, 2007 Bayer Healthcare LLC [Member] Performance-based milestone payments [Member]	Dec. 31, 2007 Bayer Healthcare LLC [Member] Upfront payment arrangement [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones	$ 161.1											$ 28.0		$ 73.1		$ 50.0
Contingent payments receivable based on development events regulatory to be pursued and completed solely by others		140.0	95.0	235.0	75.0
Deferred revenue						14.1	20.1				37.9		7.0			23.8
Received upfront and milestone payments								22.0	5.0	27.0								20.0	40.0
Performance milestone payments recorded as a liability to Bayer																10.0	10.0
Development milestones achieved															$ 10.0