v2.4.0.8
Document and Entity Information
3 Months Ended
Mar. 31, 2015
Apr. 16, 2015
Common Stock
Apr. 16, 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-Q    
Document Period End Date Mar. 31, 2015    
Document Fiscal Year Focus 2015    
Document Fiscal Period Focus Q1    
Amendment Flag false    
Entity Common Stock, Shares Outstanding   101,305,623 1,971,868