Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Narrative) (Details)

v2.4.1.9
Stockholders' Equity (Narrative) (Details) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Employee Stock Purchase Plan    
Stock-based compensation $ 2,914,000us-gaap_ShareBasedCompensation $ 2,067,000us-gaap_ShareBasedCompensation
Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Rights 1/8 on the six month anniversary of the date of grant, and 1/48 each month thereafter for 42 months  
Award Expiration Period 10 years  
Weighted-average grant date fair value of stock options $ 32.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
 
Intrinsic value of options exercised 1,900,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
12,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Unrecognized compensation cost 17,800,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
 
Weighted-average period in which cost is expected to be recognized 2 years 7 months 6 days  
Restricted Stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Period 3 years  
Weighted-average period in which cost is expected to be recognized 2 years 2 months 12 days  
Unrecognized compensation cost, restricted stock 5,700,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
 
2002 Stock Incentive Plan | Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares available for future option grants 700,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= lgnd_TwoThousandTwoStockIncentivePlanMember
 
Employee Stock Purchase Plan    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Expiration Period 6 months 6 months
Employee Stock Purchase Plan    
Shares allowed to purchase in employee stock purchase plan 1,250us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
 
Offering period of shares in employee stock purchase plan 6 months  
Percentage of purchase price of stock 85.00%lgnd_PercentageOfPurchasePriceOfStock
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
 
Discount rate 15.00%lgnd_DiscountRate
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
 
Shares issued in period 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
Stock-based compensation 21,000us-gaap_ShareBasedCompensation
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
13,000us-gaap_ShareBasedCompensation
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
Shares available for future purchases 75,741us-gaap_EmployeeServiceShareBasedCompensationEstimatedQuantityOfSharesToBeRepurchasedInFollowingPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
 
Volatility rate 36.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
38.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
Employee Stock Purchase Plan | Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Net proceeds from employee stock purchase plan 800,000us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
3,200,000us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
Tax benefit related to options exercised $ 0us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
 
Certain Directors | 2002 Stock Incentive Plan    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Period 1 year  
Employees    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Period 4 years  
Vesting Period One | 2002 Stock Incentive Plan | Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Period 6 months  
Award Vesting Rights, Percentage 12.50%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= lgnd_TwoThousandTwoStockIncentivePlanMember
/ us-gaap_VestingAxis
= lgnd_VestingPeriodOneMember
 
Vesting Period Two | 2002 Stock Incentive Plan | Stock Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Period 42 months  
Award Vesting Rights, Percentage 2.08%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= lgnd_TwoThousandTwoStockIncentivePlanMember
/ us-gaap_VestingAxis
= lgnd_VestingPeriodTwoMember