v3.10.0.1
Document and Entity Information - USD ($)
$ in Billions
12 Months Ended
Dec. 31, 2018
Feb. 04, 2019
Jun. 30, 2018
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2018    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Trading Symbol SGEN    
Entity Registrant Name SEATTLE GENETICS INC /WA    
Entity Central Index Key 0001060736    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   160,561,234  
Entity Public Float     $ 7
Entity Emerging Growth Company false    
Entity Small Business false    
Entity Shell Company false