Loans and Borrowings - Summary of Convertible Bonds (Details) - EUR (€) € in Thousands	Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about borrowings [line items]
Current convertible loans	€ 415	€ 415
Non-current convertible loans	52,206	49,861
OCEANE
Disclosure of detailed information about borrowings [line items]
Notes and debentures issued	€ 52,622	€ 50,276

The amount of current notes and debentures issued and the current portion of non-current notes and debentures issued. [Refer: Notes and debentures issued]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2023-01-01
-Paragraph 112
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2023-en-r&anchor=para_112_c&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_CurrentNotesAndDebenturesIssuedAndCurrentPortionOfNoncurrentNotesAndDebenturesIssued
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_DisclosureOfDetailedInformationAboutBorrowingsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The non-current portion of non-current notes and debentures issued. [Refer: Notes and debentures issued]

+ References

+ Details

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

- Definition

The amount of notes and debentures issued by the entity.

+ References

+ Details

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

- Details

Name:	ifrs-full_BorrowingsByNameAxis=gnft_BondsConvertibleOrExchangeableIntoNewOrExistingSharesOCEANEMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: