| Document And Entity Information | Jan. 16, 2025 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jan. 16, 2025 |
| Entity Registrant Name | Atara Biotherapeutics, Inc. |
| Entity Central Index Key | 0001604464 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-36548 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 46-0920988 |
| Entity Address, Address Line One | 2380 Conejo Spectrum Street |
| Entity Address, Address Line Two | Suite 200 |
| Entity Address, City or Town | Thousand Oaks |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 91320 |
| City Area Code | (805) |
| Local Phone Number | 623-4211 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.0001 per share |
| Trading Symbol | ATRA |
| Security Exchange Name | NASDAQ |
