v3.6.0.2
Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2016
Feb. 01, 2017
Jun. 30, 2016
Entity Information [Line Items]      
Entity Registrant Name REGENERON PHARMACEUTICALS INC    
Entity Central Index Key 0000872589    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Document Type 10-K    
Document Period End Date Dec. 31, 2016    
Document Fiscal Year Focus 2016    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Public Float     $ 35,224,000,000
Common Stock      
Entity Information [Line Items]      
Entity Common Stock, Shares Outstanding   104,169,299  
Class A Stock      
Entity Information [Line Items]      
Entity Common Stock, Shares Outstanding   1,911,456