Quarterly report pursuant to Section 13 or 15(d)

Stock-based Compensation (Details)

v2.4.1.9
Stock-based Compensation (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Stock-based awards weighted average assumptions [Abstract]    
Dividend yield (in hundredths) 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
Expected volatility (in hundredths) 82.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate 94.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
Risk free interest rate (in hundredths) 1.34%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate 1.73%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Expected term 5 years 7 months 6 days 5 years 7 months 6 days
Stock option activity [Roll Forward]    
Outstanding beginning of period (in shares) 7,702,309us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Granted (in shares) 1,322,528us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross  
Exercised (in shares) (65,815)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised  
Forfeited, expired or cancelled (in shares) (620,440)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod  
Outstanding end of period (in shares) 8,338,582us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Vested and expected to vest at end of period (in shares) 7,928,331us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber  
Exercisable at end of period (in shares) 4,621,508us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber  
Stock options activity, weighted average exercise price [Roll Forward]    
Outstanding, beginning of period (in dollars per share) $ 8.15us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice  
Granted (in dollars per share) $ 3.82us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice  
Exercised (in dollars per share) $ 1.55us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice  
Forfeited, expired or cancelled (in dollars per share) $ 25.65us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice  
Outstanding, end of period (in dollars per share) $ 6.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice  
Vested and expected to vest, end of period (in dollars per share) $ 6.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice  
Exercisable weighted average exercise price (in dollars per share) $ 7.52us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice  
Additional Disclosures [Abstract]    
Outstanding weighted average remaining contractual term beginning of period 7 years 6 months  
Outstanding weighted average remaining contractual term end of period 7 years 6 months  
Vested and expected to vest, weighted average remaining contractual term 7 years 4 months 28 days  
Exercisable weighted average remaining contractual term 6 years 4 months 2 days  
Outstanding, aggregate intrinsic value at end of period $ 3,174us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue  
Vested and expected to vest, aggregate intrinsic value 3,131us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue  
Exercisable, aggregate intrinsic value 2,409us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1  
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]    
Total stock-based compensation expense 3,665us-gaap_AllocatedShareBasedCompensationExpense 3,924us-gaap_AllocatedShareBasedCompensationExpense
Research and Development [Member]    
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]    
Total stock-based compensation expense 2,196us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember
2,406us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember
Selling, General and Administrative [Member]    
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]    
Total stock-based compensation expense $ 1,469us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember
$ 1,518us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember
Restricted Stock Units (RSUs) [Member]    
Unvested RSU activity [Roll Forward]    
Unvested balance beginning of period (in shares) 1,953,879us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Granted (in shares) 1,401,652us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Vested (in shares) (802,081)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Forfeited (in shares) (27,138)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Unvested balance end of period (in shares) 2,526,312us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Unvested RSU activity, weighted average grant date fair value [Roll Forward]    
Unvested balance, beginning of period (in dollars per share) $ 5.46us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Granted (in dollars per share) $ 3.83us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Vested (in dollars per share) $ 5.04us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Forfeited (in dollars per share) $ 5.88us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Unvested balance, end of period (in dollars per share) $ 4.69us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Long Term Incentive Plan [Member] | Stock Options [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting period 4 years  
Stock option activity [Roll Forward]    
Granted (in shares) 1,322,528us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= xoma_LongTermIncentivePlanMember
 
Long Term Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting period 3 years  
Stock option activity [Roll Forward]    
Granted (in shares) 1,401,652us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= xoma_LongTermIncentivePlanMember