Discontinued operations, consideration received.

No definition available.

Name:	clls_DiscontinuedOperationsConsiderationReceived
Namespace Prefix:	clls_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Discontinued operations, fair value of retained investment.

+ References

No definition available.

+ Details

Name:	clls_DiscontinuedOperationsFairValueOfRetainedInvestment
Namespace Prefix:	clls_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Net assets, liabilities and equity derecognized.

+ References

No definition available.

+ Details

Name:	clls_NetAssetsLiabilitiesAndEquityDerecognized
Namespace Prefix:	clls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfAnalysisOfSingleAmountOfDiscontinuedOperationsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of liabilities included in disposal groups classified as held for sale. [Refer: Liabilities; Disposal groups classified as held for sale [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 5
-IssueDate 2025-01-01
-Paragraph 38
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=5&code=ifrs-tx-2025-en-r&anchor=para_38&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 54
-Subparagraph p
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_54_p&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_LiabilitiesIncludedInDisposalGroupsClassifiedAsHeldForSale
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of equity in a subsidiary not attributable, directly or indirectly, to a parent. [Refer: Total for all subsidiaries [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 10
-IssueDate 2025-01-01
-Paragraph 22
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=10&code=ifrs-tx-2025-en-r&anchor=para_22&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2025-01-01
-Paragraph 12
-Subparagraph f
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2025-en-r&anchor=para_12_f&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 54
-Subparagraph q
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_54_q&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_NoncontrollingInterests
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of non-current assets or disposal groups classified as held for sale. [Refer: Disposal groups classified as held for sale [member]]

+ References

+ Details

Name:	ifrs-full_NoncurrentAssetsOrDisposalGroupsClassifiedAsHeldForSale
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash inflow from the disposal of non-current assets or disposal groups classified as held for sale and discontinued operations. [Refer: Discontinued operations [member]; Disposal groups classified as held for sale [member]; Non-current assets or disposal groups classified as held for sale]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2025-01-01
-Paragraph 16
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=7&code=ifrs-tx-2025-en-r&anchor=para_16&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_ProceedsFromDisposalOfNoncurrentAssetsOrDisposalGroupsClassifiedAsHeldForSaleAndDiscontinuedOperations
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 5
-IssueDate 2025-01-01
-Paragraph 33
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=5&code=ifrs-tx-2025-en-r&anchor=para_33_a&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2025-01-01
-Paragraph B12
-Subparagraph b
-Clause vii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2025-en-r&anchor=para_B12_b_vii&doctype=Appendix&subtype=B
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 98
-Subparagraph e
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_98_e&doctype=Standard
-URIDate 2025-03-27

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 82
-Subparagraph ea
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_82_ea&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_ProfitLossFromDiscontinuedOperations
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	ifrs-full_ContinuingAndDiscontinuedOperationsAxis=ifrs-full_DiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=clls_CalyxtIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Scope of consolidation and non-consolidated entities - Impact of Deconsolidation on Group's Financial Statements (Details) - USD ($) $ in Thousands		12 Months Ended
	May 31, 2023	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disclosure of analysis of single amount of discontinued operations [line items]
Profit from deconsolidation		$ 0	$ 0	$ 8,392
Discontinued operations [member] \| Calyxt Inc. [Member]
Disclosure of analysis of single amount of discontinued operations [line items]
Assets held for sale	$ (19,714)
Liabilities related to asset held for sale	23,592
Non-controlling interests	3,625
Net assets, liabilities and equity derecognized	7,503
Consideration received in cash	0
Fair value of the retained investment	15,097
Consideration received	15,097
Profit from deconsolidation	$ 22,600