v3.19.3
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Oct. 31, 2019
Document and Entity Information    
Document Type 10-Q  
Document Period End Date Sep. 30, 2019  
Entity Registrant Name Celldex Therapeutics, Inc.  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   16,130,105
Entity Central Index Key 0000744218  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Entity Ex Transition Period false