Assets Or liabilities associated with related party variable interest

No definition available.

Name:	bcab_AssetsOrLiabilitiesAssociatedWithRelatedPartyVariableInterest
Namespace Prefix:	bcab_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Description of agreement with related party.

+ References

No definition available.

+ Details

Name:	bcab_DescriptionOfAgreementWithRelatedParty
Namespace Prefix:	bcab_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Extended Rent Agreement

+ References

No definition available.

+ Details

Name:	bcab_ExtendedRentAgreement
Namespace Prefix:	bcab_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Options grants related to royalty payment, Period.

+ References

No definition available.

+ Details

Name:	bcab_OptionsGrantsRelatedToRoyaltyPaymentPeriod
Namespace Prefix:	bcab_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Options grants, related to royalty payments period.

+ References

No definition available.

+ Details

Name:	bcab_OptionsGrantsRelatedToRoyaltyPaymentsPeriod
Namespace Prefix:	bcab_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Share of Royalties under Royalty Sharing Agreement

+ References

No definition available.

+ Details

Name:	bcab_ShareOfRoyaltiesUnderRoyaltySharingAgreement
Namespace Prefix:	bcab_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_CommonStockSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow associated with the amount received from entity's raising of capital via private rather than public placement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 14
-Subparagraph (a)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-14

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfPrivatePlacement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c)(2)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c)(2)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

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

+ Details

Name:	us-gaap_ResearchAndDevelopmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of expense related to royalty payments under a contractual arrangement such as payment for mineral and drilling rights and use of technology or intellectual property.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

+ Details

Name:	us-gaap_RoyaltyExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_RelatedPartyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=bcab_NovembertwoThousandTwentyTwoUnderwrittensOfferingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=bcab_InversagenLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=bcab_HimalayaTherapeuticsSEZCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=bcab_BioAtlaHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Related party transactions - Additional Information (Details) - USD ($)		12 Months Ended
	Jul. 07, 2020	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2020	Jan. 01, 2020
Related Party Transaction [Line Items]
Research and development expense		$ 103,731,000	$ 79,347,000
Common Stock, Shares, Issued		48,077,599	46,336,166
Related Party \| November 2022 Underwritten Offering
Related Party Transaction [Line Items]
Common Stock, Shares, Issued		2,998,500
Net proceeds Issuance Of private placement		$ 19,100,000
Inversagen L L C
Related Party Transaction [Line Items]
Royalty Expense	$ 0
Options grants related to royalty payment, Period		10 years
Assets or liabilities associated with related party variable interest		$ 0	$ 0
Himalaya Therapeutics S E Z C
Related Party Transaction [Line Items]
Research and development expense		$ 100,000	400,000
Extended Rent Agreement		12 months
Royalty Expense		$ 0
Description Of Agreement With Related Party		In April 2022, the Company entered into a Clinical Trial Agreement with Himalaya Therapeutics SEZC. Under the agreement, Himalaya Therapeutics SEZC agreed to provide services related to the initiation of clinical trials for mecbotamab vedotin in the People’s Republic of China. For the first year following effectiveness of the agreement, the Company has agreed to pay Himalaya Therapeutics SEZC for the full-time use of two of its personnel. Payments were due and payable by BioAtla to Himalaya Therapeutics SEZC on a quarterly calendar basis and are non-refundable. The Company made its final payment under the agreement in January 2023. For the twelve months ended December 31, 2023 and 2022, the Company recognized $0.1 million and $0.4 million in research and development expense related to the Clinical Trial Agreement, respectively. The Company did not have any amounts due from or due to Himalaya Therapeutics SEZC as of December 31, 2023.
Assets or liabilities associated with related party variable interest				$ 0
Bio Atla Holdings L L C
Related Party Transaction [Line Items]
Assets or liabilities associated with related party variable interest		$ 0	$ 0
Options grants related to royalty payments, Period	10 years
Share of Royalties under Royalty Sharing Agreement					50.00%