Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Related Party Transaction [Line Items]
Research and development expense	$ 16,395	$ 28,400	$ 51,445	$ 81,057
Due to related party	1,800		$ 1,800
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 (as so amended, the “Clinical Trial Services Agreement”) with Himalaya Therapeutics SEZC (“Himalaya”). Under the Clinical Trial Services Agreement, BioAtla will pay Himalaya 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.Global Transaction AgreementIn September 2024, the Company entered into a Global Transaction Agreement (the “Himalaya Agreement”) with Himalaya. BioAtla and Himalaya had previously entered into an Amended and Restated Exclusive Rights Agreement (the “Amended Rights Agreement”) in January of 2020. Pursuant to the Amended Rights Agreement, Himalaya controls rights to develop, manufacture and commercialize certain assets, including BA3362 which was licensed to Context (see Note 7), in certain territories as further specified in the Amended Rights Agreement. Pursuant to the Himalaya Agreement, Himalaya consented to BioAtla’s execution and performance of the Agreement, and granted to BioAtla an exclusive, worldwide, sublicensable license for those impacted products and intellectual property. Further, as set forth in the Amended Rights Agreement and further clarified in the Himalaya Agreement, BioAtla agreed to pay, subject to any applicable tax withholdings, to Himalaya (i) a mid-teens percentage of all upfront payments and development milestones received by BioAtla from Context under the Context License Agreement; and (ii) a specified percentage of any and all sales milestones and/or royalties based upon Net Sales (as defined in the Context License Agreement) in the People’s Republic of China and the Special Administrative Regions of Hong Kong, Macao and Taiwan that BioAtla receives from Context under the Context License Agreement.The Company is the principal in the Context License Agreement and in the Himalaya Agreement, and will record revenues and expenses on a gross basis given that the Company had full discretion in setting consideration pricing in the Context License Agreement, the Company will be primarily responsible for providing the License, and Himalaya has no obligation to be a part of any of the fulfillment activities.For the three and nine months ended September 30, 2024, the Company recognized $1.8 million and $2.0 million, respectively, in research and development expense related to the transactions with Himalaya, compared to $0 and $0.1 million for the three and nine months ended September 30, 2023, respectively. As of September 30, 2024, the Company had $1.8 million due to Himalaya.
Research and development expense	$ 1,800	$ 0	$ 2,000	$ 100