Document and Entity Information
6 Months Ended
Jun. 30, 2013
Jul. 29, 2013
Document and Entity Information    
Entity Registrant Name Celldex Therapeutics, Inc.  
Entity Central Index Key 0000744218  
Document Type 10-Q  
Document Period End Date Jun. 30, 2013  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   80,987,871
Document Fiscal Year Focus 2013  
Document Fiscal Period Focus Q2