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Document and Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2024
Feb. 26, 2025
Jun. 30, 2024
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2024    
Document Fiscal Year Focus 2024    
Document Fiscal Period Focus FY    
Trading Symbol ATRA    
Entity Registrant Name ATARA BIOTHERAPEUTICS, INC.    
Entity Central Index Key 0001604464    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Non-accelerated Filer    
Entity Shell Company false    
Entity Small Business true    
Entity Emerging Growth Company false    
Entity File Number 001-36548    
Entity Tax Identification Number 46-0920988    
Entity Address, Address Line One 1280 Rancho Conejo Blvd    
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    
Entity Incorporation, State or Country Code DE    
Title of 12(b) Security Common Stock, par value $0.0001 per share    
Security Exchange Name NASDAQ    
Entity Interactive Data Current Yes    
Document Annual Report true    
Document Transition Report false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Auditor Firm ID 34    
Auditor Name DELOITTE & TOUCHE LLP    
Auditor Location San Francisco, California    
Auditor Opinion [Text Block]

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Atara Biotherapeutics, Inc. and subsidiaries (the "Company" or “Atara”) as of December 31, 2024 and 2023, the related consolidated statements of operations and comprehensive income (loss), stockholders’ equity (deficit), and cash flows, for each of the two years in the period ended December 31, 2024, and the related notes (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and 2023, and the results of its operations and its cash flows for each of the two years in the period ended December 31, 2024, in conformity with accounting principles generally accepted in the United States of America.

   
Entity Public Float     $ 41,039,683
Entity Common Stock, Shares Outstanding   5,858,909  
Documents Incorporated by Reference Portions of the Registrant’s definitive proxy statement relating to its 2025 Annual Meeting of Stockholders are incorporated by reference into Part III of this Report where indicated. Such proxy statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates.