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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 | $ 67,569 us-gaap_AvailableForSaleSecurities |  | $ 102,748 us-gaap_AvailableForSaleSecurities |  |
Gross unrealized gain (losses) on available for sale securities | 0 us-gaap_AvailableforsaleSecuritiesGrossUnrealizedGainLoss1 |  | (1,000)us-gaap_AvailableforsaleSecuritiesGrossUnrealizedGainLoss1 |  |
Carrying Value [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Outstanding debt | 35,537 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember |  | 40,985 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember |  |
Fair Value [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Outstanding debt | 36,461 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember |  | 41,813 us-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 | 69,869 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByLiabilityClassAxis = xoma_ContingentWarrantLiabilitiesMember |  | 15,001 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByLiabilityClassAxis = xoma_ContingentWarrantLiabilitiesMember |  | 379 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByLiabilityClassAxis = xoma_ContingentWarrantLiabilitiesMember
Initial fair value of warrants issued | 10,258 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues / us-gaap_FairValueByLiabilityClassAxis = xoma_ContingentWarrantLiabilitiesMember |  |  |  | 6,390 us-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 |  | 61,039 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings / us-gaap_FairValueByLiabilityClassAxis = xoma_ContingentWarrantLiabilitiesMember |  | 9,172 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings / us-gaap_FairValueByLiabilityClassAxis = xoma_ContingentWarrantLiabilitiesMember
Balance, end of period | 31,828 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByLiabilityClassAxis = xoma_ContingentWarrantLiabilitiesMember |  | 69,869 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByLiabilityClassAxis = xoma_ContingentWarrantLiabilitiesMember |  | 15,001 us-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 | 67,569 xoma_MoneyMarketFundsFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | [1] | 82,759 xoma_MoneyMarketFundsFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | [1] |
U.S. treasury securities |  |  | 19,989 xoma_USTreasurySecuritiesFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Foreign exchange options | 6 us-gaap_ForeignCurrencyContractAssetFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 361 us-gaap_ForeignCurrencyContractAssetFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Total | 67,575 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 103,109 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Liabilities: [Abstract] |  |  |  |  |
Contingent warrant liabilities | 31,828 us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 69,869 us-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 | 67,569 xoma_MoneyMarketFundsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | [1] | 82,759 xoma_MoneyMarketFundsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | [1] |
U.S. treasury securities |  |  | 19,989 xoma_USTreasurySecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Foreign exchange options | 0 us-gaap_ForeignCurrencyContractAssetFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 0 us-gaap_ForeignCurrencyContractAssetFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Total | 67,569 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 102,748 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Liabilities: [Abstract] |  |  |  |  |
Contingent warrant liabilities | 0 us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 0 us-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 | 0 xoma_MoneyMarketFundsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | [1] | 0 xoma_MoneyMarketFundsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | [1] |
U.S. treasury securities |  |  | 0 xoma_USTreasurySecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Foreign exchange options | 6 us-gaap_ForeignCurrencyContractAssetFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 361 us-gaap_ForeignCurrencyContractAssetFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Total | 6 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 361 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Liabilities: [Abstract] |  |  |  |  |
Contingent warrant liabilities | 0 us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 0 us-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 | 0 xoma_MoneyMarketFundsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | [1] | 0 xoma_MoneyMarketFundsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | [1] |
U.S. treasury securities |  |  | 0 xoma_USTreasurySecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Foreign exchange options | 0 us-gaap_ForeignCurrencyContractAssetFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 0 us-gaap_ForeignCurrencyContractAssetFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Total | 0 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 0 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Liabilities: [Abstract] |  |  |  |  |
Contingent warrant liabilities | 31,828 us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 69,869 us-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 | 67,569 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember |  | 82,759 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember |  |
US Treasury Securities [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available-for-sale securities | $ 0 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember |  | $ 19,989 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasurySecuritiesMember |  |
[1] | Included in cash and cash equivalents

X
- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
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- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes money market funds included in cash and cash equivalents. + References No definition available. + Details
Name: | xoma_MoneyMarketFundsFairValueDisclosure
Namespace Prefix: | xoma_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition This category includes information about debt securities issued by the United States Department of the Treasury and backed by the United States government. Such securities primarily consist of treasury bills (short-term maturities - one year or less), treasury notes (intermediate term maturities - two to ten years), and treasury bonds (long-term maturities - ten to thirty years). + References No definition available. + Details
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Namespace Prefix: | xoma_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |