Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation (Narrative) (Details)

v2.4.1.9
Basis of Presentation (Narrative) (Details) (USD $)
Share data in Millions, unless otherwise specified
3 Months Ended 1 Months Ended 12 Months Ended
Mar. 31, 2015
segment
storage_location
drug
Mar. 31, 2014
Apr. 30, 2013
program
Jan. 31, 2012
Jan. 31, 2010
right
Dec. 31, 2013
customer
Dec. 31, 2014
Apr. 30, 2014
Jan. 31, 2011
Aug. 31, 2014
Property, Plant and Equipment [Line Items]                    
Net income $ 754,000us-gaap_NetIncomeLoss $ 2,097,000us-gaap_NetIncomeLoss                
Accumulated deficit 658,561,000us-gaap_RetainedEarningsAccumulatedDeficit           659,315,000us-gaap_RetainedEarningsAccumulatedDeficit      
Working capital 173,600,000lgnd_WorkingCapital                  
Earnings (Loss) Per Share                    
Common shares excluded from computation 4.5us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount 1.0us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount                
Cash, Cash Equivalents and Short-term Investments                    
Maturity period of cash and cash equivalents, maximum 3 months                  
Maturity period of short term investments, minimum 3 months                  
Concentrations of Credit Risk                    
Cash deposits 107,300,000lgnd_CashDepositsInExcessOfFdicInsuredAmount           91,700,000lgnd_CashDepositsInExcessOfFdicInsuredAmount      
Product Shelf Life 5 years                  
Number of Storage Locations 3us-gaap_NumberOfStores                  
Allowance for Doubtful Accounts                    
Accounts receivable outstanding considered past due after period, minimum 30 days                  
Accounts receivable outstanding considered past due after period, maximum 90 days                  
Allowance for doubtful accounts 0us-gaap_AllowanceForDoubtfulAccountsReceivable           0us-gaap_AllowanceForDoubtfulAccountsReceivable      
Property and Equipment                    
Depreciation 100,000us-gaap_Depreciation 100,000us-gaap_Depreciation                
Goodwill and Other Identifiable Intangible Assets                    
Finite-lived intangible asset, useful life 20 years                  
Amortization expense 600,000us-gaap_AmortizationOfIntangibleAssets 600,000us-gaap_AmortizationOfIntangibleAssets                
Amortization Expense                    
Amortization expense 2015 2,400,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear                  
Amortization expense 2016 2,400,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo                  
Amortization expense 2017 2,400,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree                  
Amortization expense 2018 2,400,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour                  
Amortization expense 2019 2,400,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive                  
Revenue Recognition                    
Period allowed for return of products, minimum 30 days                  
Period allowed for return of products, maximum 90 days                  
Restocking fee (percent) 20.00%lgnd_SalesReturnsRestockingFeePercent                  
Discontinued Operations                    
Number of drugs included in product line 4lgnd_NumberOfDrugsIncludedInProductLine                  
Segment Reporting                    
Number of reportable segments 2us-gaap_NumberOfReportableSegments                  
Consolidation of Variable Interest Entities                    
Assets 263,223,000us-gaap_Assets           258,029,000us-gaap_Assets      
Liabilities 230,828,000us-gaap_Liabilities           233,621,000us-gaap_Liabilities      
Minimum                    
Revenue Recognition                    
Period when partenr sales reports are received after end of quarter 30 days                  
Maximum                    
Revenue Recognition                    
Period when partenr sales reports are received after end of quarter 60 days                  
Equipment | Minimum                    
Property and Equipment                    
Estimated useful life of assets 3 years                  
Equipment | Maximum                    
Property and Equipment                    
Estimated useful life of assets 10 years                  
Royalty Stream and Milestone Payments Purchase Agreement with Selexis                    
Commercial License Rights                    
Number of commercial license agreement programs (programs)     15lgnd_LicenseAgreementNumberofCommercialLicenseAgreementPrograms
/ us-gaap_BusinessAcquisitionAxis
= lgnd_RoyaltyStreamAndMilestonePaymentsPurchaseAgreementWithSelexisMember
             
Purchase price     4,600,000lgnd_LicenseAgreementPurchasePriceNetofAcquisitionCosts
/ us-gaap_BusinessAcquisitionAxis
= lgnd_RoyaltyStreamAndMilestonePaymentsPurchaseAgreementWithSelexisMember
             
Payments to acquire intangible assets     3,600,000us-gaap_PaymentsToAcquireIntangibleAssets
/ us-gaap_BusinessAcquisitionAxis
= lgnd_RoyaltyStreamAndMilestonePaymentsPurchaseAgreementWithSelexisMember
             
Cash payment due on first anniversary of the closing               1,000,000lgnd_LicenseAgreementCashPaymentDueOnFirstAnniversaryOfClosing
/ us-gaap_BusinessAcquisitionAxis
= lgnd_RoyaltyStreamAndMilestonePaymentsPurchaseAgreementWithSelexisMember
   
Cydex Pharmaceuticals, Inc                    
Contingent Liabilities                    
Contingent liability                 17,600,000us-gaap_BusinessCombinationContingentConsiderationLiability
/ us-gaap_BusinessAcquisitionAxis
= lgnd_CydexPharmaceuticalsIncMember
 
Fair value of liability 9,400,000lgnd_BusinessAcquisitionContingentConsiderationPotentialCashPaymentAtEndOfPeriod
/ us-gaap_BusinessAcquisitionAxis
= lgnd_CydexPharmaceuticalsIncMember
          11,500,000lgnd_BusinessAcquisitionContingentConsiderationPotentialCashPaymentAtEndOfPeriod
/ us-gaap_BusinessAcquisitionAxis
= lgnd_CydexPharmaceuticalsIncMember
     
Contingent liability change in amount 1,200,000us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1
/ us-gaap_BusinessAcquisitionAxis
= lgnd_CydexPharmaceuticalsIncMember
500,000us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1
/ us-gaap_BusinessAcquisitionAxis
= lgnd_CydexPharmaceuticalsIncMember
               
Cydex Pharmaceuticals, Inc | Guaranteed Payment                    
Contingent Liabilities                    
Purchase of commercial license rights       4,300,000us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
/ us-gaap_BusinessAcquisitionAxis
= lgnd_CydexPharmaceuticalsIncMember
/ us-gaap_ContingentConsiderationByTypeAxis
= lgnd_GuaranteedPaymentMember
           
Cydex Pharmaceuticals, Inc | Revenue Sharing                    
Contingent Liabilities                    
Purchase of commercial license rights 3,200,000us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
/ us-gaap_BusinessAcquisitionAxis
= lgnd_CydexPharmaceuticalsIncMember
/ us-gaap_ContingentConsiderationByTypeAxis
= lgnd_RevenueSharingMember
1,600,000us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
/ us-gaap_BusinessAcquisitionAxis
= lgnd_CydexPharmaceuticalsIncMember
/ us-gaap_ContingentConsiderationByTypeAxis
= lgnd_RevenueSharingMember
               
Metabasis Therapeutics                    
Contingent Liabilities                    
Fair value of liability 2,500,000lgnd_BusinessAcquisitionContingentConsiderationPotentialCashPaymentAtEndOfPeriod
/ us-gaap_BusinessAcquisitionAxis
= lgnd_MetabasisTherapeuticsMember
          3,700,000lgnd_BusinessAcquisitionContingentConsiderationPotentialCashPaymentAtEndOfPeriod
/ us-gaap_BusinessAcquisitionAxis
= lgnd_MetabasisTherapeuticsMember
     
Contingent liability change in amount 1,200,000us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1
/ us-gaap_BusinessAcquisitionAxis
= lgnd_MetabasisTherapeuticsMember
(2,500,000)us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1
/ us-gaap_BusinessAcquisitionAxis
= lgnd_MetabasisTherapeuticsMember
               
Number of contingent value rights         4lgnd_NumberOfContingentValueRightsIssued
/ us-gaap_BusinessAcquisitionAxis
= lgnd_MetabasisTherapeuticsMember
         
Number of contingent value rights per series of contingent value rights         1lgnd_NumberOfContingentValueRightsPerSeriesOfContingentValueRights
/ us-gaap_BusinessAcquisitionAxis
= lgnd_MetabasisTherapeuticsMember
         
Number of contingent value rights issued for each share         4lgnd_NumberOfRespectiveSeriesOfContingentValueRightsIssuedForEachShare
/ us-gaap_BusinessAcquisitionAxis
= lgnd_MetabasisTherapeuticsMember
         
Contingent value rights, frequency of cash payment         6 months          
Accounts Receivable | Customer Concentration Risk                    
Concentrations of Credit Risk                    
Concentration risk, number of customers 3lgnd_ConcentrationRiskNumberOfCustomers
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
        2lgnd_ConcentrationRiskNumberOfCustomers
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
       
Concentration risk, percentage of accounts receivable 77.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
        64.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
       
Acquired In Process Research And Development                    
Acquired In-Process Research and Development                    
Impairment of in-process research and development 0lgnd_WriteoffofInProcessResearchandDevelopment
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= lgnd_AcquiredInProcessResearchAndDevelopmentMember
0lgnd_WriteoffofInProcessResearchandDevelopment
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= lgnd_AcquiredInProcessResearchAndDevelopmentMember
               
Omthera Pharmaceuticals                    
Milestone Payments                    
Event-based payment 1,000,000us-gaap_RevenueRecognitionMilestoneMethodRevenueRecognized
/ dei_LegalEntityAxis
= lgnd_OmtheraPharmaceuticalsMember
                 
Proceeds from Collaborators             500,000us-gaap_ProceedsFromCollaborators
/ dei_LegalEntityAxis
= lgnd_OmtheraPharmaceuticalsMember
     
Viking                    
Consolidation of Variable Interest Entities                    
Assets 2,768,000us-gaap_Assets
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
          3,043,000us-gaap_Assets
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
     
Liabilities 5,521,000us-gaap_Liabilities
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
          4,953,000us-gaap_Liabilities
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
     
Collaborative Arrangement, Product | Omthera Pharmaceuticals                    
Milestone Payments                    
Event-based payment             400,000us-gaap_RevenueRecognitionMilestoneMethodRevenueRecognized
/ dei_LegalEntityAxis
= lgnd_OmtheraPharmaceuticalsMember
/ us-gaap_TypeOfArrangementAxis
= us-gaap_CollaborativeArrangementProductAgreementMember
     
2019 convertible senior notes                    
Convertible Debt                    
Principal amount outstanding 245,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= lgnd_A2019ConvertibleSeniorNotesMember
          245,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= lgnd_A2019ConvertibleSeniorNotesMember
     
2019 convertible senior notes | Senior Notes                    
Convertible Debt                    
Principal amount outstanding                   $ 245,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= lgnd_A2019ConvertibleSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Interest rate                   0.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= lgnd_A2019ConvertibleSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember