| Document and Entity Information | Mar. 09, 2023 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | XOMA Corp |
| Entity Incorporation State Country Code | DE |
| Amendment Flag | false |
| Entity Central Index Key | 0000791908 |
| Document Type | 8-K |
| Document Period End Date | Mar. 09, 2023 |
| Entity File Number | 001-39801 |
| Entity Tax Identification Number | 52-2154066 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock, $0.0075 par value |
| Trading Symbol | XOMA |
| Security Exchange Name | NASDAQ |
| Series A Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 8.625% Series A Cumulative Perpetual Preferred Stock, par value $0.05 per share |
| Trading Symbol | XOMAP |
| Security Exchange Name | NASDAQ |
| Series B Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Depositary Shares (each representing 1/1000th interest in a share of 8.375% Series B Cumulative Perpetual Preferred Stock, par value $0.05 per share) |
| Trading Symbol | XOMAO |
| Security Exchange Name | NASDAQ |
