Quarterly report pursuant to Section 13 or 15(d)

Condensed Consolidated Financial Statements Detail (Details)

v2.4.1.9
Condensed Consolidated Financial Statements Detail (Details) (USD $)
 3 Months Ended 12 Months Ended 1 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Mar. 31, 2012
Feb. 28, 2010
May 05, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]            
Antidilutive securities excluded from computation of earnings per share (in shares) 29,446,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount 7,642,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount        
Numerator [Abstract]            
Net loss, Basic $ (21,718,000)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments $ (4,687,000)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments        
Adjustment for revaluation of contingent warrant liabilities 0xoma_AmountOfDilutiveSecuritiesForRevaluationOfContingentWarrantLiabilities (19,534,000)xoma_AmountOfDilutiveSecuritiesForRevaluationOfContingentWarrantLiabilities        
Net loss, Diluted (21,718,000)us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted (24,221,000)us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted        
Denominator Abstract]            
Weighted average shares outstanding used for basic net loss per share (in shares) 116,193,000us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 106,158,000us-gaap_WeightedAverageNumberOfSharesOutstandingBasic        
Effect of dilutive warrants (in shares) 0us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants 9,366,000us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants        
Weighted average shares outstanding and dilutive securities used to diluted net income per share (in shares) 116,193,000us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 115,524,000us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding        
Accrued and other liabilities [Abstract]            
Accrued payroll and other benefits 2,578,000us-gaap_AccruedSalariesCurrent   3,061,000us-gaap_AccruedSalariesCurrent      
Accrued management incentive compensation 1,149,000us-gaap_AccruedBonusesCurrent   4,295,000us-gaap_AccruedBonusesCurrent      
Accrued clinical trial costs 1,079,000xoma_AccruedClinicalTrialCosts   1,424,000xoma_AccruedClinicalTrialCosts      
Other 1,186,000us-gaap_OtherAccruedLiabilitiesCurrent   1,112,000us-gaap_OtherAccruedLiabilitiesCurrent      
Total 5,992,000us-gaap_AccruedLiabilitiesCurrent   9,892,000us-gaap_AccruedLiabilitiesCurrent [1]      
Two Year Warrants Issued in December 2014 [Member]            
Class of Warrant or Right [Line Items]            
Warrants outstanding (in shares)     8,097,165us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_TwoYearWarrantsIssuedInDecember2014Member 		     
Exercise price of warrants (in dollars per share)     $ 7.90us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_TwoYearWarrantsIssuedInDecember2014Member 		     
Fair value of warrant liability 4,800,000us-gaap_WarrantsNotSettleableInCashFairValueDisclosure
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_TwoYearWarrantsIssuedInDecember2014Member 		  5,200,000us-gaap_WarrantsNotSettleableInCashFairValueDisclosure
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_TwoYearWarrantsIssuedInDecember2014Member 		     
Gain (loss) on revaluation of warrant liability 400,000us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_TwoYearWarrantsIssuedInDecember2014Member 		         
Warrant term     2 years      
Five Year Warrants Issued in March 2012 [Member]            
Class of Warrant or Right [Line Items]            
Warrants outstanding (in shares) 12,109,418us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedSecondRangeMember 		  12,109,418us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedSecondRangeMember 		14,834,577us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedSecondRangeMember 		   
Exercise price of warrants (in dollars per share)       $ 1.76us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedSecondRangeMember 		   
Fair value of warrant liability 27,000,000us-gaap_WarrantsNotSettleableInCashFairValueDisclosure
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedSecondRangeMember 		  26,700,000us-gaap_WarrantsNotSettleableInCashFairValueDisclosure
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedSecondRangeMember 		     
Gain (loss) on revaluation of warrant liability (300,000)us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedSecondRangeMember 		19,500,000us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedSecondRangeMember 		       
Warrant term       5 years    
Five Year Warrants Issued in February 2010 [Member]            
Class of Warrant or Right [Line Items]            
Warrants outstanding (in shares)         1,260,000us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedFirstRangeMember 		 
Exercise price of warrants (in dollars per share)         $ 10.50us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= xoma_FiveYearWarrantsIssuedFirstRangeMember 		 
Warrant term         5 years  
Subsequent Event [Member]            
Class of Warrant or Right [Line Items]            
Cashless exercise of warrants (in shares)           1,470,000xoma_CashlessExerciseOfWarrantsShares
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
Warrants issued (in shares)           785,192xoma_WarrantsIssued
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
Demand Deposits [Member]            
Cash and Cash Equivalents [Line Items]            
Cash equivalents 7,400,000us-gaap_CashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= us-gaap_DemandDepositsMember 		  10,800,000us-gaap_CashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= us-gaap_DemandDepositsMember 		     
Money Market Funds [Member]            
Cash and Cash Equivalents [Line Items]            
Cash equivalents $ 60,100,000us-gaap_CashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= us-gaap_MoneyMarketFundsMember 		  $ 67,600,000us-gaap_CashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= us-gaap_MoneyMarketFundsMember 		     
Common Stock Options and Restricted Stock [Member]            
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]            
Antidilutive securities excluded from computation of earnings per share (in shares) 8,756,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= xoma_CommonStockOptionsAndRestrictedStockUnitsMember 		5,732,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= xoma_CommonStockOptionsAndRestrictedStockUnitsMember 		       
Warrants for Common Stock [Member]            
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]            
Antidilutive securities excluded from computation of earnings per share (in shares) 20,690,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_WarrantMember 		1,910,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_WarrantMember 		       
[1] The condensed consolidated balance sheet as of December 31, 2014 has been derived from the audited consolidated financial statements as of that date included in the Company 's Annual Report on Form 10-K for the year ended December 31, 2014.