Other Current Liabilities - Additional Information (Detail) $ in Millions	6 Months Ended
Jun. 30, 2023 USD ($)
Other current liabilities [abstract]
Decrease in other current liabilities	$ 5.1

Decrease in other current liabilities related to asset suppliers.

No definition available.

Name:	clls_DecreaseInOtherCurrentLiabilitiesRelatedToAssetSuppliers
Namespace Prefix:	clls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration