License and Collaboration Agreements - Additional Information (Details) - USD ($)			1 Months Ended		3 Months Ended
	Feb. 13, 2018	Aug. 23, 2017	Apr. 30, 2018	Sep. 30, 2017	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable					$ 30,220,000		$ 22,492,000
Bristol Myers Squibb Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable					26,900,000		$ 21,400,000
Bristol Myers Squibb Company | Purchase Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shares issued (in shares)			8,284,600
Sale of stock consideration received			$ 850,000,000
Other Partner
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones (up to)					40,000,000
Nektar-358 | Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received upfront and milestone payment				$ 150,000,000
Percentage of sharing in Phase 2 development costs		25.00%
Nektar-358 | Eli Lilly And Company | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional development and regulatory milestones (up to)		$ 250,000,000
Nektar-358 | Eli Lilly And Company | Nektar's
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-358 | Eli Lilly And Company | Nektar's | 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%
Nektar-358 | Eli Lilly
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing in Phase 2 development costs		75.00%
Nektar 214 | Bristol Myers Squibb Company | Research and Development Expense
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses					$ 24,900,000	$ 26,700,000
Nektar 214 | Bristol Myers Squibb Collaboration Agreement | Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing production costs	65.00%
Upfront and milestone payments received from license agreements			$ 1,000,000,000
Nektar 214 | Bristol Myers Squibb Collaboration Agreement | Nektar's | Milestone One
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones (up to)								$ 50,000,000
Nektar 214 | Bristol Myers Squibb Collaboration Agreement | Bristol Myers Squibb Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing production costs	35.00%
Nektar 214 | Opdivo | Bristol Myers Squibb Collaboration Agreement | Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	32.50%
Nektar 214 | Opdivo | Bristol Myers Squibb Collaboration Agreement | Bristol Myers Squibb Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	67.50%