License and Collaboration Agreements - License, Collaboration and Other Revenue (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 30,127	$ 36,289	$ 124,372
Roche [Member] | PEGASYS and MIRCERA [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	7,146	5,131	5,131
Baxter Healthcare [Member] | Hemophilia [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	6,238	5,646	1,701
Amgen, Inc. [Member] | Neulasta [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	5,000	5,000	833
Bayer Healthcare LLC [Member] | BAY41-6551 (Amikacin Inhale) [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	2,971	2,992	3,300
Affymax, Inc. [Member] | OMONTYS [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	2,829	3,838	1,867
AstraZeneca AB [Member] | Naloxegol (NKTR-118) and naloxegol fixed-dose combination program (NKTR-119) [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	59	2,496	107,854
Other [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 5,884	$ 11,186	$ 3,686