Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Related Party Transaction [Line Items]
Research and development expense	$ 18,852	$ 21,697
Due to related party	$ 100
Himalaya Therapeutics SEZC
Related Party Transaction [Line Items]
Description of agreement with related party	In January 2024, the Company entered into an amended Clinical Trial Services Agreement with Himalaya Therapeutics SEZC (as so amended, the “Clinical Trial Services Agreement”). Under the Clinical Trial Services Agreement, BioAtla will pay Himalaya Therapeutics SEZC for the full-time use of two of its personnel and provide services related to the initiation of clinical trials for evalstotug in China for a period of 12 months. For the three months ended March 31, 2024 and 2023, the Company recognized $0.1 million and $0.1 million, respectively, in research and development expense related to the Clinical Trial Services Agreement. As of March 31, 2024, the Company had $0.1 million due to Himalaya Therapeutics SEZC, related to the Clinical Trial Services Agreement.
Research and development expense	$ 100

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 730
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482916/730-10-50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 912
-SubTopic 730
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482517/912-730-25-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481283/985-20-50-1

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