XOMA Corporation Quarterly report pursuant to Section 13 or 15(d)

Subsequent Events - Additional Information (Details) $ in Millions			1 Months Ended
	Apr. 14, 2018 USD ($) Facility	Nov. 21, 2017 USD ($) Facility	Oct. 31, 2018 USD ($) Facility	Nov. 30, 2018 USD ($)
Subsequent Event [Line Items]
Operating leases, number of portions of leased facilities \| Facility	1	1
Operating leases, number of leased facilities \| Facility	3	3
Operating leases, sublease commencement date	May 01, 2018	Dec. 26, 2017
Operating leases sublease income receivable \| $	$ 1.1	$ 5.1
Operating leases sublease expiry date	2023-04	2023-04
Forecast [Member] \| Maximum [Member] \| BVF [Member]
Subsequent Event [Line Items]
Amount of securities agreed to sold in rights offering \| $				$ 20.0
Forecast [Member] \| Holders of Common Stock and Series X Preferred Stock [Member] \| Maximum [Member]
Subsequent Event [Line Items]
Rights offring amount \| $				$ 20.0
Subsequent Event [Member]
Subsequent Event [Line Items]
Operating leases, number of portions of leased facilities \| Facility			1
Operating leases, number of leased facilities \| Facility			3
Operating leases, sublease commencement date			Oct. 24, 2018
Operating leases sublease income receivable \| $			$ 1.7
Operating leases sublease expiry date			2021-05