Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2023	Feb. 14, 2024	Jun. 30, 2023
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	000-15006
Entity Registrant Name	CELLDEX THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-3191702
Entity Address, Address Line One	Perryville III Building
Entity Address, Address Line Two	53 Frontage Road
Entity Address, Address Line Three	Suite 220
Entity Address, City or Town	Hampton
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08827
City Area Code	908
Local Phone Number	200-7500
Title of 12(b) Security	Common Stock, par value $.001
Trading Symbol	CLDX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 1.6
Entity Common Stock, Shares Outstanding		55,900,679
Entity Central Index Key	0000744218
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Boston, Massachusetts
Auditor Firm ID	238