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

Capital Stock - ATM Agreements (Details) - USD ($) $ in Millions				20 Months Ended	51 Months Ended
	Aug. 05, 2021	Mar. 10, 2021	Dec. 18, 2018	Mar. 31, 2023	Mar. 31, 2023
2018 Common Stock ATM Agreement \| Maximum
Sale of stock
Sales commission paid per transaction (as a percent)			3.00%
2021 ATM Agreement \| Series B Depositary Shares
Sale of stock
Shares issued (in shares)				0
Maximum amount of shares to be issued	$ 50.0
2021 ATM Agreement \| Maximum
Sale of stock
Sales commission paid per transaction, preferred stock (as a percent)	3.00%
Common Stock \| 2018 Common Stock ATM Agreement
Sale of stock
Shares issued (in shares)					0
Maximum amount of shares to be issued		$ 50.0	$ 30.0