Annual report pursuant to Section 13 and 15(d)

Available-for-Sale and Fair Value Measurements (Details)

v2.4.1.9
Available-for-Sale and Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale securities $ 67,569us-gaap_AvailableForSaleSecurities $ 102,748us-gaap_AvailableForSaleSecurities  
Gross unrealized gain (losses) on available for sale securities 0us-gaap_AvailableforsaleSecuritiesGrossUnrealizedGainLoss1 (1,000)us-gaap_AvailableforsaleSecuritiesGrossUnrealizedGainLoss1  
Carrying Value [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Outstanding debt 35,537us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember 		40,985us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember 		 
Fair Value [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Outstanding debt 36,461us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember 		41,813us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember 		 
Warrant Liabilities [Member]      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Balance, beginning of period 69,869us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember 		15,001us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember 		379us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
Initial fair value of warrants issued 10,258us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember 		  6,390us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
Reclassification of contingent warrant liability to equity upon exercise of warrants (2,526)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember 		(6,171)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember 		(940)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
Net increase (decrease) in fair value of contingent warrant liabilities upon revaluation (45,773)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember 		61,039us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember 		9,172us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
Balance, end of period 31,828us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember 		69,869us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember 		15,001us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
Warrant Liabilities [Member] | Minimum [Member]      
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]      
Expected volatility (in hundredths) 69.60%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember 		66.10%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember 		 
Risk-free interest rate (in hundredths) 0.03%us-gaap_FairValueAssumptionsRiskFreeInterestRate
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember 		0.10%us-gaap_FairValueAssumptionsRiskFreeInterestRate
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember 		 
Expected term 0 years 1 month 2 days 0 years 10 months 24 days  
Warrant Liabilities [Member] | Maximum [Member]      
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]      
Expected volatility (in hundredths) 72.90%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		86.60%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		 
Risk-free interest rate (in hundredths) 0.67%us-gaap_FairValueAssumptionsRiskFreeInterestRate
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		0.80%us-gaap_FairValueAssumptionsRiskFreeInterestRate
/ us-gaap_FairValueByLiabilityClassAxis
= xoma_ContingentWarrantLiabilitiesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		 
Expected term 2 years 2 months 8 days 3 years 2 months 12 days  
Recurring [Member]      
Assets: [Abstract]      
Money market funds 67,569xoma_MoneyMarketFundsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1] 82,759xoma_MoneyMarketFundsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1]  
U.S. treasury securities   19,989xoma_USTreasurySecuritiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Foreign exchange options 6us-gaap_ForeignCurrencyContractAssetFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		361us-gaap_ForeignCurrencyContractAssetFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Total 67,575us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		103,109us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Liabilities: [Abstract]      
Contingent warrant liabilities 31,828us-gaap_OtherLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		69,869us-gaap_OtherLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]      
Assets: [Abstract]      
Money market funds 67,569xoma_MoneyMarketFundsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1] 82,759xoma_MoneyMarketFundsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1]  
U.S. treasury securities   19,989xoma_USTreasurySecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Foreign exchange options 0us-gaap_ForeignCurrencyContractAssetFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		0us-gaap_ForeignCurrencyContractAssetFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Total 67,569us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		102,748us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Liabilities: [Abstract]      
Contingent warrant liabilities 0us-gaap_OtherLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		0us-gaap_OtherLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]      
Assets: [Abstract]      
Money market funds 0xoma_MoneyMarketFundsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1] 0xoma_MoneyMarketFundsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1]  
U.S. treasury securities   0xoma_USTreasurySecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Foreign exchange options 6us-gaap_ForeignCurrencyContractAssetFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		361us-gaap_ForeignCurrencyContractAssetFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Total 6us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		361us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Liabilities: [Abstract]      
Contingent warrant liabilities 0us-gaap_OtherLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		0us-gaap_OtherLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]      
Assets: [Abstract]      
Money market funds 0xoma_MoneyMarketFundsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1] 0xoma_MoneyMarketFundsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		[1]  
U.S. treasury securities   0xoma_USTreasurySecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Foreign exchange options 0us-gaap_ForeignCurrencyContractAssetFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		0us-gaap_ForeignCurrencyContractAssetFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Total 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Liabilities: [Abstract]      
Contingent warrant liabilities 31,828us-gaap_OtherLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		69,869us-gaap_OtherLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember 		 
Money Market Funds [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale securities 67,569us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember 		82,759us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember 		 
US Treasury Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale securities $ 0us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasurySecuritiesMember 		$ 19,989us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasurySecuritiesMember 		 
[1] Included in cash and cash equivalents