Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2023	Mar. 20, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
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	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
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
Entity Public Float			$ 161,602,451
Entity Common Stock, Shares Outstanding		119,359,230
Documents Incorporated by Reference	Portions of the Registrant’s definitive proxy statement relating to its 2024 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.