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

Capital Stock - ATM Agreements (Details) - USD ($) $ in Millions						8 Months Ended	39 Months Ended
	Aug. 05, 2021	Apr. 09, 2021	Mar. 10, 2021	Dec. 15, 2020	Dec. 18, 2018	Mar. 31, 2022	Mar. 31, 2022
8.625% Series A Cumulative, Perpetual Preferred Stock
Sale of stock
Shares issued (in shares)				984,000
Series B Depositary Shares
Sale of stock
Shares issued (in shares)		1,600,000
2018 Common Stock ATM Agreement
Sale of stock
Maximum amount of common shares to be issued					$ 30.0
Shares issued (in shares)							0
Maximum amount of shares to be issued			$ 50.0
2018 Common Stock ATM Agreement \| Maximum
Sale of stock
Sales commission paid per transaction (as a percent)					3.00%
2021 ATM Agreement
Sale of stock
Maximum amount of common shares to be issued	$ 50.0
2021 ATM Agreement \| Series B Depositary Shares
Sale of stock
Shares issued (in shares)						0
2021 ATM Agreement \| Maximum
Sale of stock
Sales commission paid per transaction, preferred stock (as a percent)	3.00%