Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v3.10.0.1
Document and Entity Information - USD ($)
$ in Billions
12 Months Ended
Dec. 31, 2018
Feb. 25, 2019
Jun. 30, 2018
Document and Entity Information [Abstract]      
Entity Registrant Name LIGAND PHARMACEUTICALS INC    
Entity Central Index Key 0000886163    
Document Type 10-K    
Document Period End Date Dec. 31, 2018    
Amendment Flag false    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Entity Emerging Growth Company false    
Entity Small Business false    
Entity Shell Company false    
Entity Common Stock, Shares Outstanding   20,445,407  
Entity Public Float     $ 3.6
Entity Voluntary Filers No    
Entity Well-Known Seasoned Issuer Yes    
Entity Current Reporting Status Yes