Annual report pursuant to Section 13 and 15(d)

Quarterly Financial Information (unaudited) (Details)

v2.4.1.9
Quarterly Financial Information (unaudited) (Details) (USD $)
 3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Quarterly Financial Information (unaudited) [Abstract]                      
Total revenues $ 4,347,000us-gaap_Revenues $ 5,136,000us-gaap_Revenues $ 5,973,000us-gaap_Revenues $ 3,410,000us-gaap_Revenues $ 12,535,000us-gaap_Revenues $ 6,312,000us-gaap_Revenues $ 7,151,000us-gaap_Revenues $ 9,453,000us-gaap_Revenues $ 18,866,000us-gaap_Revenues $ 35,451,000us-gaap_Revenues $ 33,782,000us-gaap_Revenues
Total operating costs and expenses (23,475,000)us-gaap_OperatingExpenses [1] (25,589,000)us-gaap_OperatingExpenses [1] (24,750,000)us-gaap_OperatingExpenses [1] (26,884,000)us-gaap_OperatingExpenses [1] (28,114,000)us-gaap_OperatingExpenses (23,535,000)us-gaap_OperatingExpenses (21,230,000)us-gaap_OperatingExpenses (20,777,000)us-gaap_OperatingExpenses (100,698,000)us-gaap_OperatingExpenses (93,656,000)us-gaap_OperatingExpenses (90,406,000)us-gaap_OperatingExpenses
Other income (expense), net 11,810,000us-gaap_NonoperatingIncomeExpense [2] 6,054,000us-gaap_NonoperatingIncomeExpense [2] 6,880,000us-gaap_NonoperatingIncomeExpense [2] 18,787,000us-gaap_NonoperatingIncomeExpense [2] (36,719,000)us-gaap_NonoperatingIncomeExpense [2] (12,416,000)us-gaap_NonoperatingIncomeExpense [2] (3,169,000)us-gaap_NonoperatingIncomeExpense [2] (13,563,000)us-gaap_NonoperatingIncomeExpense [2]      
Income tax benefit (expense) 0us-gaap_IncomeTaxExpenseBenefit 0us-gaap_IncomeTaxExpenseBenefit 0us-gaap_IncomeTaxExpenseBenefit 0us-gaap_IncomeTaxExpenseBenefit (1,000)us-gaap_IncomeTaxExpenseBenefit 15,000us-gaap_IncomeTaxExpenseBenefit 0us-gaap_IncomeTaxExpenseBenefit 0us-gaap_IncomeTaxExpenseBenefit 0us-gaap_IncomeTaxExpenseBenefit 14,000us-gaap_IncomeTaxExpenseBenefit 74,000us-gaap_IncomeTaxExpenseBenefit
Net loss (7,318,000)us-gaap_NetIncomeLoss (14,399,000)us-gaap_NetIncomeLoss (11,897,000)us-gaap_NetIncomeLoss (4,687,000)us-gaap_NetIncomeLoss (52,299,000)us-gaap_NetIncomeLoss (29,624,000)us-gaap_NetIncomeLoss (17,248,000)us-gaap_NetIncomeLoss (24,887,000)us-gaap_NetIncomeLoss (38,301,000)us-gaap_NetIncomeLoss (124,058,000)us-gaap_NetIncomeLoss (71,065,000)us-gaap_NetIncomeLoss
Basic net loss per share of common stock (in dollars per share) $ (0.07)us-gaap_EarningsPerShareBasic $ (0.13)us-gaap_EarningsPerShareBasic $ (0.11)us-gaap_EarningsPerShareBasic $ (0.04)us-gaap_EarningsPerShareBasic         $ (0.36)us-gaap_EarningsPerShareBasic $ (1.43)us-gaap_EarningsPerShareBasic $ (1.10)us-gaap_EarningsPerShareBasic
Diluted net loss per share of common stock (in dollars per share) $ (0.12)us-gaap_EarningsPerShareDiluted $ (0.17)us-gaap_EarningsPerShareDiluted $ (0.17)us-gaap_EarningsPerShareDiluted $ (0.21)us-gaap_EarningsPerShareDiluted         $ (0.67)us-gaap_EarningsPerShareDiluted $ (1.43)us-gaap_EarningsPerShareDiluted $ (1.10)us-gaap_EarningsPerShareDiluted
Basic and diluted net loss per share of common stock         $ (0.55)us-gaap_EarningsPerShareBasicAndDiluted $ (0.34)us-gaap_EarningsPerShareBasicAndDiluted $ (0.21)us-gaap_EarningsPerShareBasicAndDiluted $ (0.30)us-gaap_EarningsPerShareBasicAndDiluted      
Restatement Adjustment [Member]                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Decrease to operating expenses (1,600,000)xoma_QuantifyingMisstatementInCurrentYearFinancialStatementsAmountOperatingExpenses
/ us-gaap_StatementScenarioAxis
= us-gaap_RestatementAdjustmentMember 		                   
Decrease to net loss $ (1,600,000)xoma_QuantifyingMisstatementInCurrentYearFinancialStatementsAmountNetIncomeLoss
/ us-gaap_StatementScenarioAxis
= us-gaap_RestatementAdjustmentMember 		                   
Decrease to basic loss per share (in dollar per shares) $ (0.01)xoma_QuantifyingMisstatementInCurrentYearFinancialStatementsEarningsPerShareBasic
/ us-gaap_StatementScenarioAxis
= us-gaap_RestatementAdjustmentMember 		                   
Decrease to diluted loss per share (in dollar per shares) $ (0.02)xoma_QuantifyingMisstatementInCurrentYearFinancialStatementsEarningsPerShareDiluted
/ us-gaap_StatementScenarioAxis
= us-gaap_RestatementAdjustmentMember 		                   
[1] In 2014, the Company corrected an immaterial error driven by certain stock-based compensation expense in the fourth quarter of 2014, resulting in a decrease to operating expenses and net loss by $1.6 million and a decrease to basic and diluted loss per share of $0.01 and $0.02, respectively, for the three months ended December 31, 2014. Refer to Note 2, Basis of Presentation and Significant Accounting Policies - Correction of an Immaterial Error
[2] Fluctuations in 2014 and 2013 primarily relate to (losses) gains on the revaluation of the contingent warrant liabilities.