Represents the Business Combination Contingent Consideration Contractual Credit In Merger Agreement.

No definition available.

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

- Definition

Represents the business combination contingent consideration settlement agreement amount paid.

+ References

No definition available.

+ Details

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

- Definition

Represents the business combination contingent consideration settlement agreement amount payable.

+ References

No definition available.

+ Details

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

- Definition

Number of shares of equity interests issued or issuable to acquire entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI https://asc.fasb.org/extlink&oid=126975305&loc=d3e6927-128479

+ Details

Name:	us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-URI https://asc.fasb.org/extlink&oid=126975305&loc=d3e6927-128479

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=cldx_EuropeanMedicinesAgencyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=cldx_ClinicalTrailMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ContingentConsiderationByTypeAxis=cldx_ContingentMilestoneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=cldx_KolltanPharmaceuticalsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Kolltan Acquisition (Details) - USD ($) $ in Millions	Jun. 20, 2022	Nov. 29, 2016
Kolltan Acquisition
Execution of the settlement agreement	$ 15.0
European medicines agency
Kolltan Acquisition
Business contingent amount payable	52.5
Clinical Trial
Kolltan Acquisition
Execution of the settlement agreement	15.0
Contractual credit merger agreement	2.5
Specified development, regulatory approvals or sales-based milestones
Kolltan Acquisition
Business contingent amount payable	$ 172.5
Kolltan
Kolltan Acquisition
Shares issued as part of consideration (in shares)		1,217,200
Kolltan \| Specified development, regulatory approvals or sales-based milestones
Kolltan Acquisition
Potential milestone payments		$ 172.5