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

- Definition

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

+ References

No definition available.

+ Details

Name:	us-gaap_LitigationSettlementExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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 ($)			6 Months Ended
Kolltan Acquisition (Details) - USD ($)	Jun. 20, 2022	Nov. 29, 2016	Jun. 30, 2022
Kolltan Acquisition
Execution of the settlement agreement	$ 15,000,000
Litigation Settlement, Expense			$ 15,000,000
European medicines agency
Kolltan Acquisition
Business contingent amount payable	52,500,000
Clinical Trail [Member]
Kolltan Acquisition
Execution of the settlement agreement	15,000,000
Litigation Settlement, Expense			$ 15,000,000.0
Contractual credit merger agreement	2,500,000
Specified development, regulatory approvals or sales-based milestones
Kolltan Acquisition
Business contingent amount payable	$ 172,500,000
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		$ 172,500,000