Royalty and Commercial Payment Purchase Agreements - Under Cost Recovery Method (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Royalty and Commercial Payment Purchase Agreements
Short-term royalty and commercial payment receivables under the cost recovery method	$ 0	$ 413
Long-term royalty and commercial payment receivables under the cost recovery method	$ 55,888	$ 55,936

Royalty and commercial payment receivables under cost recovery method probable and reasonably estimable to be received after one year or beyond the normal operating cycle, if longer.

No definition available.

Name:	xoma_RoyaltyAndCommercialPaymentReceivablesCostRecoveryMethodLongTerm
Namespace Prefix:	xoma_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant