License and Collaboration Agreements - Additional Information (Details) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Feb. 13, 2018	Jul. 23, 2017	Apr. 30, 2018	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net expense reimbursements from collaboration partner							$ 21,400
Accounts receivable					$ 5,981	$ 5,981	22,492
Bristol Myers Squibb Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable					4,200	4,200
Bristol-Myers Squibb | Purchase Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shares issued (in shares)			8,284,600
Sale of stock consideration received			$ 850,000
Other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones					40,000	40,000
Nektar 214 | Bristol-Myers Squibb
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses					$ 20,800
Nektar 214 | Bristol-Myers Squibb | Research and Development
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses				$ 24,900		$ 45,700	$ 101,500	$ 128,200
Bristol Myers Squibb Collaboration Agreement | Nektar 214 | Bristol-Myers Squibb
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing production costs	35.00%
Bristol Myers Squibb Collaboration Agreement | Nektar 214 | Bristol-Myers Squibb | Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	67.50%
Nektar-358 | Eli Lilly
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing in Phase 2 development costs		75.00%
Nektar-358 | Eli Lilly And Company | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional development and regulatory milestones		$ 250,000
Nektar's | Bristol Myers Squibb Collaboration Agreement | Nektar 214
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing production costs	65.00%
Upfront and milestone payments received from license agreements			1,000,000
Nektar's | Bristol Myers Squibb Collaboration Agreement | Nektar 214 | Milestone One
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones			$ 50,000
Nektar's | Bristol Myers Squibb Collaboration Agreement | Nektar 214 | Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	32.50%
Nektar's | Nektar-358
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received upfront and milestone payment		$ 150,000
Percentage of sharing in Phase 2 development costs		25.00%
Nektar's | Nektar-358 | Eli Lilly And Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of regulatory milestones payments will be reduced under certain conditions		50.00%
Percentage of regulatory milestones payments will be reduced if conditions occur		75.00%
Nektar's | Nektar-358 | Eli Lilly And Company | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of funding phase 3 development costs on an indication by indication basis borne		25.00%