Restructuring, Impairment and Other Costs of Terminated Program - Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2022 employee	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2022 employee
Restructuring Cost and Reserve [Line Items]
Impairment expense for facilities		$ 1.2
Measurement Input, Market Participant Subtenant Borrowing Rate
Restructuring Cost and Reserve [Line Items]
Operating lease, measurement input				6.40%
Nektar 214 | Bristol Myers Squibb Company
Restructuring Cost and Reserve [Line Items]
Reimbursement of expenses		$ 8.3		$ 16.7
Nektar 214 | Research and Development Expense | Bristol Myers Squibb Company
Restructuring Cost and Reserve [Line Items]
Reimbursement of expenses			$ 24.3	$ 24.9	$ 76.5
Employee Severance
Restructuring Cost and Reserve [Line Items]
Workforce termination, percentage	70.00%
Number of employees | employee	225					735