Subsequent Event	12 Months Ended
Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Event	Note 14 — Subsequent Event On February 13, 2018, we entered into the BMS Collaboration Agreement with BMS, pursuant to which we and BMS will jointly develop NKTR-214, including, without limitation, in combination with BMS’s Opdivo^® (nivolumab) and Opdivo^® plus Yervoy^® (ipilimumab), and other compounds of BMS, us or any third party. The parties have agreed to jointly commercialize NKTR-214 on a worldwide basis. BMS will pay us a non-refundable upfront cash payment of $1.0 billion. We are eligible to receive additional cash payments of a total of up to $1.43 billion upon achievement of certain development and regulatory milestones and a total of up to $350.0 million upon achievement of certain sales milestones. We will book all worldwide sales and revenue for NKTR-214. We will share global commercialization profits and losses with BMS for NKTR-214, with Nektar sharing 65% and BMS sharing 35% of the net profits and losses. BMS will lead commercialization for combinations of NKTR-214 with BMS proprietary medicines, and we will lead all other commercialization efforts for NKTR-214. We will have the final decision-making authority regarding the pricing for NKTR-214. NKTR-214 will be sold on a stand-alone basis and there will be no fixed-dose combinations or co-packaging without the consent of both parties. Under the BMS Collaboration Agreement, we and BMS will collaborate to develop and conduct clinical studies of NKTR-214 pursuant to a joint development plan, which initially includes a series of registration-enabling trials in more than 20 indications in nine tumor types and may be updated and expanded only upon mutual agreement of the parties. The parties will share the development costs for NKTR-214 in combination regimens based on each party’s relative ownership interest in the compounds included in the regimens. Pursuant to a Share Purchase Agreement entered into by us and BMS on February 13, 2018 (Purchase Agreement), BMS has also agreed to purchase 8,284,600 shares of our common stock for total cash consideration of $850.0 million, or $102.60 per share. The closing of the share purchase is subject to the expiration or early termination of the waiting period (and any extension thereof) under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 and other customary closing conditions. The closings of the BMS Collaboration Agreement and the Purchase Agreement will be simultaneous and are expected to occur during the second quarter of 2018.

Note 14 — Subsequent Event

On February 13, 2018, we entered into the BMS Collaboration Agreement with BMS, pursuant to which we and BMS will jointly develop NKTR-214, including, without limitation, in combination with BMS’s Opdivo^® (nivolumab) and Opdivo^® plus Yervoy^® (ipilimumab), and other compounds of BMS, us or any third party. The parties have agreed to jointly commercialize NKTR-214 on a worldwide basis. BMS will pay us a non-refundable upfront cash payment of $1.0 billion. We are eligible to receive additional cash payments of a total of up to $1.43 billion upon achievement of certain development and regulatory milestones and a total of up to $350.0 million upon achievement of certain sales milestones. We will book all worldwide sales and revenue for NKTR-214. We will share global commercialization profits and losses with BMS for NKTR-214, with Nektar sharing 65% and BMS sharing 35% of the net profits and losses. BMS will lead commercialization for combinations of NKTR-214 with BMS proprietary medicines, and we will lead all other commercialization efforts for NKTR-214. We will have the final decision-making authority regarding the pricing for NKTR-214. NKTR-214 will be sold on a stand-alone basis and there will be no fixed-dose combinations or co-packaging without the consent of both parties. Under the BMS Collaboration Agreement, we and BMS will collaborate to develop and conduct clinical studies of NKTR-214 pursuant to a joint development plan, which initially includes a series of registration-enabling trials in more than 20 indications in nine tumor types and may be updated and expanded only upon mutual agreement of the parties. The parties will share the development costs for NKTR-214 in combination regimens based on each party’s relative ownership interest in the compounds included in the regimens.

Pursuant to a Share Purchase Agreement entered into by us and BMS on February 13, 2018 (Purchase Agreement), BMS has also agreed to purchase 8,284,600 shares of our common stock for total cash consideration of $850.0 million, or $102.60 per share. The closing of the share purchase is subject to the expiration or early termination of the waiting period (and any extension thereof) under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 and other customary closing conditions. The closings of the BMS Collaboration Agreement and the Purchase Agreement will be simultaneous and are expected to occur during the second quarter of 2018.