v3.10.0.1
Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2018
Feb. 20, 2019
Jun. 30, 2018
Document and Entity Information [Abstract]      
Entity Registrant Name IONIS PHARMACEUTICALS INC    
Entity Central Index Key 0000874015    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Shell Company false    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Ex Transition Period false    
Entity Public Float     $ 4,805,287,142
Entity Common Stock, Shares Outstanding   138,397,754  
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2018    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY