Other Long-Term Liabilities (Details 2) (USD $)	3 Months Ended	1 Months Ended	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013 Rockefeller Development Services Agreement	Mar. 31, 2014 Rockefeller Development Services Agreement
Other Long-Term Liabilities
Approved project plan for the development services			$ 4,800,000
Term of the agreement			3 years
Upfront payment recognized as revenue over the term of the agreement			1,300,000
Contracts and Grants	$ 381,000	$ 50,000		$ 400,000

This element represents revenue earned during the period arising from products sold or services provided under the terms of a contract. Also include revenue earned during the period from non-repayable sum of money awarded to an entity to carry out a specific purpose as provided in grant agreements.

No definition available.

Name:	cldx_RevenueFromContractsAndGrants
Namespace Prefix:	cldx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration