Related party transactions - Additional Information (Details) - USD ($)			12 Months Ended
	Mar. 23, 2021	Jul. 07, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2020
Related Party Transaction [Line Items]
Research and development expense			$ 79,347,000	$ 58,274,000
Related party transaction, terms and manner of settlement			(i) a lump sum payment equal to 18 months of Ms. Anderson Short’s then-current base salary, (ii) a payment at her targeted bonus rate for 2021, pro-rated to the date of her termination of employment, and (iii) full accelerated vesting of her equity awards including 7,747 stock options and 138,461 restricted stock units. The modification of these equity awards resulted in an incremental fair value of $7.0 million which was recognized on a straight-line basis over the transition service period which ended on the separation date. For the year ended December 31, 2021, the Company recognized $1.0 million related to the lump sum salary payment and target bonus. The Company also recognized non-cash stock-based compensation charges of $9.4 million related to the modified equity awards for the year ended December 31, 2021. No unrecognized stock-based compensation related to the transition agreement was recognized for the year ended December 31, 2022.
Non-cash stock-based compensation charges			$ 14,563,000	$ 25,117,000
Common Stock, Shares, Issued			46,336,166	35,799,233
Exercised, Number of Shares			0	7,747
Forfeited, Number of Shares			2,736,918	1,086,902	615,106
Carolyn Anderson Short
Related Party Transaction [Line Items]
Number of accelerated full vesting equity awards including stock options	7,747
Number of accelerated full vesting equity awards including restricted stock units	138,461
Incremental Fair Value				$ 7,000,000.0
Expense related to Lump Sum Salary Payment and Target Bonus				1,000,000.0
Non-cash stock-based compensation charges				$ 9,400,000
Unrecognized stock-based compensation			$ 0
Private Placement of Common Stock
Related Party Transaction [Line Items]
Common Stock, Shares, Issued				625,000
Net proceeds Issuance Of private placement				$ 17,500,000
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			400,000
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 BA3011 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 are due and payable by BioAtla to Himalaya Therapeutics SEZC on a quarterly calendar basis and are non-refundable. For the twelve months ended December 31, 2022, the Company recognized $0.4 million in research and development expense related to the Clinical Trial Agreement. The Company did not have any amounts due from or due to Himalaya Therapeutics SEZC as of December 31, 2022.
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
Equity Interest In Related Party						50.00%