v2.4.0.8
Document and Entity Information (USD $)
12 Months Ended
Dec. 31, 2014
Jun. 30, 2014
Feb. 05, 2015
Common Stock
Feb. 05, 2015
Class A Stock
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, 2014      
Document Fiscal Year Focus 2014      
Document Fiscal Period Focus FY      
Amendment Flag false      
Entity Common Stock, Shares Outstanding     100,645,094 1,971,868
Entity Well-known Seasoned Issuer Yes      
Entity Voluntary Filers No      
Entity Current Reporting Status Yes      
Entity Public Float   $ 27,323,000,000