Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Nov. 01, 2019
Document And Entity Information [Abstract]    
Entity Registrant Name XOMA Corp  
Trading Symbol XOMA  
Entity Central Index Key 0000791908  
Current Fiscal Year End Date --12-31  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   8,752,269
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2019  
Entity Current Reporting Status Yes  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Tax Identification Number 52-2154066  
Entity File Number 0-14710  
Entity Address, Address Line One 2200 Powell Street  
Entity Address, Address Line Two Suite 310  
Entity Address, City or Town Emeryville  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94608  
City Area Code (510)  
Local Phone Number 204-7200  
Document Quarterly Report true  
Document Transition Report false  
Title of 12(b) Security Common Stock, $0.0075 par value  
Security Exchange Name NASDAQ  
Entity Incorporation, State or Country Code DE  
Entity Interactive Data Current Yes