| Cover | 6 Months Ended |
| Jun. 30, 2019 | |
| Cover [Abstract] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Amendment Description | This Amendment No. 1 to the Current Report on Form 8-K amends Item 8.01 of the Current Report on Form 8-K previously filed on July 25, 2019 to confirm that Nektar Therapeutics, a Delaware corporation ("Nektar") did not receive an action letter from the FDA regarding Nektar's NDA for NKTR-181, and as previously reported, Nektar continues to work with the FDA on the review of the NDA. |
| Document Period End Date | Jul. 23, 2019 |
| Entity File Number | 0-24006 |
| Entity Registrant Name | NEKTAR THERAPEUTICS |
| Entity Central Index Key | 0000906709 |
| Entity Tax Identification Number | 94-3134940 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 455 Mission Bay Boulevard South |
| Entity Address, City or Town | San Francisco |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94158 |
| City Area Code | (415) |
| Local Phone Number | 482-5300 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.0001 par value |
| Trading Symbol | NKTR |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Elected Not To Use the Extended Transition Period | false |
