Balance Sheet Details - Schedule of Accounts Payable and Accrued Expenses (Parenthetical) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2024	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Accrued research and development includes related party amounts	$ 1,775	$ 0

Accrued Research And Development Includes Related Party Amount

No definition available.

Name:	bcab_AccruedResearchAndDevelopmentIncludesRelatedPartyAmount
Namespace Prefix:	bcab_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration