Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2020
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Common Stock As discussed in Note 10, on April 3, 2018, we completed the issuance and sale of 8,284,600 shares of our common stock under a Share Purchase Agreement with BMS. These shares are unregistered and subject to certain lock-up and stand-still provisions for a five-year period. Equity Compensation Plans At December 31, 2020, we had approximately 29,784,000 reserved shares of common stock, all of which are reserved for issuance under our equity compensation plans, of which approximately 20,894,000 shares may be issued upon the exercise of outstanding options or the vesting of restricted stock units (RSUs) or performance stock units, approximately 7,569,000 shares are available for grant under our 2017 Performance Incentive Plan and approximately 1,321,000 shares are available for grant under our Employee Stock Purchase Plan. 2017 Performance Incentive Plan Our 2017 Performance Incentive Plan (2017 Plan) was adopted by our board of directors (Board of Directors) on March 28, 2017 and was approved by our stockholders on June 14, 2017. On the date of approval, any shares of our common stock that were available for issuance under our 2012 Performance Incentive Plan (2012 Plan) ceased to be available for future grants. However, options and restricted stock units granted under the 2012 Plan remained outstanding. Subject to the terms of the 2017 Plan, 8,300,000 shares of our common stock, reduced by the number of shares of common stock subject to awards granted under the 2012 Plan on or after March 31, 2017 and prior to the adoption of the 2017 Plan, were initially available for awards under the 2017 Plan. On June 26, 2018, our stockholders approved an amendment to the 2017 Plan whereby 10,900,000 additional shares were made available for award grants under the 2017 Plan (Amended Plan). On June 17, 2020, the stockholders of Nektar approved an amendment to the Amended Plan to increase the aggregate number of shares of Common Stock authorized for issuance thereunder by 10,000,000 shares (Amended and Restated 2017 Plan). Shares issued in respect of any “full-value award” granted under the 2017 Plan will be counted against the share limit described above as 1.5 shares for every one share actually issued in connection with the award. Shares that are subject to or underlie awards which expire or for any reason are cancelled or terminated, are forfeited, fail to vest, or for any other reason are not paid or delivered under the 2017 Plan or the 2012 Plan will again be available for subsequent awards under the 2017 Plan (with any such shares subject to full-value awards increasing the 2017 Plan’s share limit based on the full-value award ratio described above). Notwithstanding the foregoing, shares that are exchanged by a participant or withheld by us to pay the exercise price of an option granted under the 2017 Plan, as well as any shares exchanged or withheld to satisfy the tax withholding obligations related to any award, will not be available for subsequent awards under the 2017 Plan. The purpose of the current Amended and Restated 2017 Plan and our other incentive plans is to promote our success by providing an additional means for us to attract, motivate, retain and reward directors, officers, employees, and other eligible persons through the grant of awards. Equity-based awards are also intended to further align the interests of award recipients and our stockholders. The Amended and Restated 2017 Plan authorizes stock options, stock appreciation rights, stock bonuses, restricted stock, performance stock, stock units, phantom stock or similar rights to purchase or acquire shares, and other forms of awards granted or denominated in our common stock or units of our common stock, as well as cash bonus awards. Members of the Board of Directors, officers or employees, certain consultants and advisors and our subsidiaries are eligible to receive awards under the Amended and Restated 2017 Plan. Pursuant to the Amended and Restated 2017 Plan, we have granted or issued non-qualified stock options, RSUs and PSUs to employees, officers, and non-employee directors. The requisite service period for stock options granted to our employees under the Amended and Restated 2017 Plan as well as our prior plans is generally four years; the requisite service period for stock options granted to our directors is generally one year. The requisite service period for RSUs and PSUs granted under the Amended and Restated 2017 Plan and our prior plans is generally three years for employees and one year for directors. The Amended and Restated 2017 Plan will terminate on March 27, 2027, unless earlier terminated by the Board of Directors. The maximum term of a stock option or stock appreciation right under the Amended and Restated 2017 Plan and our prior plans is eight years from the date of grant. The per share exercise price of an option generally may not be less than the fair market value of a share of our common stock on the NASDAQ Stock Market on the date of grant. Employee Stock Purchase Plan In February 1994, our Board of Directors adopted the Employee Stock Purchase Plan (ESPP) pursuant to section 423(b) of the Internal Revenue Code of 1986. Under the ESPP, 2,500,000 shares of our common stock were originally authorized for issuance. On June 17, 2020, the stockholders of Nektar approved an amendment and restatement of the Amended and Restated Employee Stock Purchase Plan to increase the aggregate number of shares of Common Stock authorized for issuance under the plan by 1,000,000 shares. The terms of the ESPP provide eligible employees with the opportunity to acquire an ownership interest in Nektar through participation in a program of periodic payroll deductions for the purchase of our common stock. Employees may elect to enroll or re-enroll in the ESPP on a semi-annual basis. Stock is purchased at 85% of the lower of the closing price on the first day of the enrollment period or the last day of the enrollment period. 401(k) Retirement Plan We sponsor a 401(k) retirement plan whereby eligible employees may elect to contribute up to the lesser of 60% of their annual compensation or the statutorily prescribed annual limit allowable under Internal Revenue Service regulations. The 401(k) plan permits us to make matching contributions on behalf of all participants, up to a maximum of $6,000 per participant. For the years ended December 31, 2020, 2019, and 2018, we recognized $3.5 million, $3.5 million, and $2.8 million, respectively, of compensation expense in connection with our 401(k) retirement plan. Change in Control Severance Plan On December 6, 2006, our Board of Directors approved a Change of Control Severance Benefit Plan (CIC Plan). This CIC Plan has subsequently been amended a number of times by our Board of Directors with the most recent amendment occurring on April 5, 2011. The CIC Plan is designed to make certain benefits available to our eligible employees in the event of a change of control of Nektar and, following such change of control, an employee’s employment with us or a successor company is terminated in certain specified circumstances. We adopted the CIC Plan to support the continuity of the business in the context of a change of control transaction. The CIC Plan was not adopted in contemplation of any specific change of control transaction. Under the CIC Plan, in the event of a change of control of Nektar and a subsequent termination of employment initiated by us or a successor company other than for Cause (as defined in the CIC Plan) or initiated by the employee for a Good Reason Resignation (as defined in the CIC Plan) in each case within twelve months following a change of control transaction, (i) the Chief Executive Officer would be entitled to receive cash severance pay equal to 24 months base salary plus annual target incentive pay, the extension of employee benefits over this severance period and the full acceleration of unvested outstanding equity awards, and (ii) our Senior Vice Presidents and Vice Presidents (including Principal Fellows) would each be entitled to receive cash severance pay equal to twelve months base salary plus annual target incentive pay, the extension of employee benefits over this severance period and the full acceleration of unvested outstanding equity awards. In the event of a change of control of Nektar and a subsequent termination of employment initiated by the Company or a successor company other than for Cause within twelve months following a change of control transaction, all other employees would each be entitled to receive cash severance pay equal to 6 months base salary plus a pro-rata portion of annual target incentive pay, the extension of employee benefits over this severance period and the full acceleration of each such employee’s unvested outstanding equity awards. Under the CIC Plan, as amended, non-employee directors would also be entitled to full acceleration of vesting of all outstanding stock awards in the event of a change of control transaction.