XOMA Corporation Annual report pursuant to Section 13 and 15(d)

Subsequent Event - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Jan. 31, 2018	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Proceeds from issuance of common stock			$ 10,160,000	$ 57,000	$ 171,000
Common Stock [Member]
Subsequent Event [Line Items]
Sale of shares		1,200,000	1,849,000	13,000
2015 ATM Agreement [Member]
Subsequent Event [Line Items]
Proceeds from issuance of common stock			$ 600,000	$ 56,000
2015 ATM Agreement [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Sale of shares			110,252	10,365	0
Subsequent Event [Member] \| 2015 ATM Agreement [Member]
Subsequent Event [Line Items]
Proceeds from issuance of common stock	$ 2,300,000
Subsequent Event [Member] \| 2015 ATM Agreement [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Sale of shares	67,658