Subsequent Events	12 Months Ended
Dec. 31, 2011
Subsequent Events [Abstract]
Subsequent Events	Note 14 — Subsequent Events *Sale of CIMZIA^® and MIRCERA^® Royalties* On February 24, 2012, we entered into a Purchase and Sale Agreement (the "Purchase and Sale Agreement") with RPI Finance Trust ("RPI"), an affiliate of Royalty Pharma, pursuant to which, on February 29, 2012, we sold, and RPI purchased, our right to receive royalty payments (the "Royalty Entitlement") arising in respect of worldwide net sales, from and after January 1, 2012, of (a) CIMZIA^®, under Nektar's license, manufacturing and supply agreement with UCB, and (b) MIRCERA^®, under Nektar's license, manufacturing and supply agreement with Roche. We received an aggregate cash purchase price for the Royalty Entitlement of $124.0 million. Additionally, we incurred approximately $4.5 million in transaction costs. Pursuant to the Purchase and Sale Agreement, we are required to pay to RPI (a) $3.0 million if certain worldwide net sales thresholds of MIRCERA^® for the 12 month period ending on December 31, 2012 are not achieved and (b) up to an additional $7.0 million if certain worldwide net sales thresholds of MIRCERA^® for the 12 month period ending on December 31, 2013 are not achieved. The Purchase and Sale Agreement grants RPI the right to receive certain reports and other information relating to the Royalty Entitlement and contains other representations and warranties, covenants and indemnification obligations that are customary for a transaction of this nature. In particular, if we breach our obligations under the Purchase and Sale Agreement, we may be required to pay damages to RPI that could potentially exceed the purchase price. Except as described above, RPI is entitled only to the future royalty payments arising from sales of CIMZIA^® and MIRCERA^®. However, we have significant continuing involvement in the generation of these future royalty payments through our ongoing manufacturing and supply obligations to UCB and Roche. As a result, we will record a long-term liability on our consolidated balance sheet equal to the fair value of the Purchase and Sale Agreement, which approximates the up-front purchase price, and will amortize the liability using the effective interest rate method over its estimated life. As a result of this liability accounting, even though the royalties from UCB and Roche will be remitted directly to RPI, we will continue to record revenue for these royalties. The model used to estimate the fair value of the rights sold to RPI requires us to make estimates regarding, among other things, the assumptions market participants would make regarding the timing and probability of achieving the royalties, as well as the appropriate discount rates. The effective interest rate under the agreement is estimated to be approximately 17%. During the years ended December 31, 2011, 2010, and 2009, we recognized $8.3 million, $5.4 million, and $2.7 million, respectively, in aggregate royalties from net sales of MIRCERA^® and CIMZIA^®. We intend to use the net proceeds of this agreement to in part repay the $215.0 million aggregate amount of outstanding 3.25% Convertible Subordinated Notes due September 28, 2012. *Roche MIRCERA^® Manufacturing Agreement* On February 28, 2012, we entered into a toll-manufacturing agreement with Roche under which we will manufacture the proprietary PEGylation material for MIRCERA^®. Roche entered into the toll-manufacturing agreement with the objective of establishing us as a secondary back-up source on a non-exclusive basis. Under the terms of the toll-manufacturing agreement, Roche agreed to pay us an up-front payment of $5.0 million plus a total of up to $22.0 million in performance-based milestone payments upon our achievement of certain manufacturing readiness, validation and production milestones which are scheduled to be completed by the end of January 2013. There is a risk that we will not meet one or more of the milestones on a timely basis or at all. Roche will also pay us additional consideration for any future orders of the PEGylation materials for MIRCERA^® beyond the initial quantities scheduled to be manufactured and supplied in 2012. Roche may terminate the toll-manufacturing agreement due to an uncured material default by us or for convenience under certain circumstances and subject to certain financial obligations.

Note 14 — Subsequent Events

Sale of CIMZIA^® and MIRCERA^® Royalties

On February 24, 2012, we entered into a Purchase and Sale Agreement (the "Purchase and Sale Agreement") with RPI Finance Trust ("RPI"), an affiliate of Royalty Pharma, pursuant to which, on February 29, 2012, we sold, and RPI purchased, our right to receive royalty payments (the "Royalty Entitlement") arising in respect of worldwide net sales, from and after January 1, 2012, of (a) CIMZIA^®, under Nektar's license, manufacturing and supply agreement with UCB, and (b) MIRCERA^®, under Nektar's license, manufacturing and supply agreement with Roche. We received an aggregate cash purchase price for the Royalty Entitlement of $124.0 million. Additionally, we incurred approximately $4.5 million in transaction costs.

Pursuant to the Purchase and Sale Agreement, we are required to pay to RPI (a) $3.0 million if certain worldwide net sales thresholds of MIRCERA^® for the 12 month period ending on December 31, 2012 are not achieved and (b) up to an additional $7.0 million if certain worldwide net sales thresholds of MIRCERA^® for the 12 month period ending on December 31, 2013 are not achieved. The Purchase and Sale Agreement grants RPI the right to receive certain reports and other information relating to the Royalty Entitlement and contains other representations and warranties, covenants and indemnification obligations that are customary for a transaction of this nature. In particular, if we breach our obligations under the Purchase and Sale Agreement, we may be required to pay damages to RPI that could potentially exceed the purchase price.

Except as described above, RPI is entitled only to the future royalty payments arising from sales of CIMZIA^® and MIRCERA^®. However, we have significant continuing involvement in the generation of these future royalty payments through our ongoing manufacturing and supply obligations to UCB and Roche. As a result, we will record a long-term liability on our consolidated balance sheet equal to the fair value of the Purchase and Sale Agreement, which approximates the up-front purchase price, and will amortize the liability using the effective interest rate method over its estimated life. As a result of this liability accounting, even though the royalties from UCB and Roche will be remitted directly to RPI, we will continue to record revenue for these royalties. The model used to estimate the fair value of the rights sold to RPI requires us to make estimates regarding, among other things, the assumptions market participants would make regarding the timing and probability of achieving the royalties, as well as the appropriate discount rates. The effective interest rate under the agreement is estimated to be approximately 17%.

During the years ended December 31, 2011, 2010, and 2009, we recognized $8.3 million, $5.4 million, and $2.7 million, respectively, in aggregate royalties from net sales of MIRCERA^® and CIMZIA^®.

We intend to use the net proceeds of this agreement to in part repay the $215.0 million aggregate amount of outstanding 3.25% Convertible Subordinated Notes due September 28, 2012.

Roche MIRCERA^® Manufacturing Agreement

On February 28, 2012, we entered into a toll-manufacturing agreement with Roche under which we will manufacture the proprietary PEGylation material for MIRCERA^®. Roche entered into the toll-manufacturing agreement with the objective of establishing us as a secondary back-up source on a non-exclusive basis. Under the terms of the toll-manufacturing agreement, Roche agreed to pay us an up-front payment of $5.0 million plus a total of up to $22.0 million in performance-based milestone payments upon our achievement of certain manufacturing readiness, validation and production milestones which are scheduled to be completed by the end of January 2013. There is a risk that we will not meet one or more of the milestones on a timely basis or at all. Roche will also pay us additional consideration for any future orders of the PEGylation materials for MIRCERA^® beyond the initial quantities scheduled to be manufactured and supplied in 2012. Roche may terminate the toll-manufacturing agreement due to an uncured material default by us or for convenience under certain circumstances and subject to certain financial obligations.