Deferred upfront payment.

No definition available.

Name:	gnft_DeferredUpfrontPayment
Namespace Prefix:	gnft_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Non-refundable upfront payment.

+ References

No definition available.

+ Details

Name:	gnft_NonRefundableUpfrontPayment
Namespace Prefix:	gnft_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of segment.

+ References

No definition available.

+ Details

Name:	gnft_NumberOfSegment
Namespace Prefix:	gnft_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum amount of potential clinical, regulatory and commercial milestone payments.

+ References

No definition available.

+ Details

Name:	gnft_PotentialClinicalRegulatoryAndCommercialMilestonePaymentsMaximum
Namespace Prefix:	gnft_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Upfront payment received.

+ References

No definition available.

+ Details

Name:	gnft_UpfrontPaymentReceived
Namespace Prefix:	gnft_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

The amount of liabilities related to the entity's leases. Lease is a contract, or part of a contract, that conveys the right to use an underlying asset for a period of time in exchange for consideration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2019-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2019-en-r&anchor=para_47_b&doctype=Standard
-URIDate 2019-03-27

+ Details

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

- Definition

The amount of revenue that was included in the contract liability balance at the beginning of the period. [Refer: Contract liabilities; Revenue from contracts with customers]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 15
-IssueDate 2019-01-01
-Paragraph 116
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=15&code=ifrs-tx-2019-en-r&anchor=para_116_b&doctype=Standard
-URIDate 2019-03-27

+ Details

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

- Definition

The amount of assets that represent a lessee's right to use an underlying asset for the lease term. Underlying asset is an asset that is the subject of a lease, for which the right to use that asset has been provided by a lessor to a lessee.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2019-01-01
-Paragraph 53
-Subparagraph j
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2019-en-r&anchor=para_53_j&doctype=Standard
-URIDate 2019-03-27

+ Details

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

- Definition

The useful life, measured as period of time, used for intangible assets other than goodwill. [Refer: Intangible assets other than goodwill]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2019-01-01
-Paragraph 118
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=38&code=ifrs-tx-2019-en-r&anchor=para_118_a&doctype=Standard
-URIDate 2019-03-27

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average lessee's incremental borrowing rate applied to lease liabilities recognised in the statement of financial position at the date of initial application of IFRS 16. The incremental borrowing rate is the rate of interest that a lessee would have to pay to borrow over a similar term, and with a similar security, the funds necessary to obtain an asset of a similar value to the right-of-use asset in a similar economic environment.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2019-01-01
-Paragraph C12
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2019-en-r&anchor=para_C12_a&doctype=Appendix&subtype=C
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_WeightedAverageLesseesIncrementalBorrowingRateAppliedToLeaseLiabilitiesRecognisedAtDateOfInitialApplicationOfIFRS16
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=ifrs-full_ComputerSoftwareMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
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Period Type:

Summary of Significant Accounting Policies - Additional Information (Details) € in Thousands, $ in Millions		12 Months Ended
	Jul. 03, 2019 USD ($)	Dec. 31, 2019 USD ($) Segment	Jan. 01, 2019 EUR (€)	Dec. 31, 2018 EUR (€)
Disclosure Of Voluntary Change In Accounting Policy [Line Items]
Non-refundable upfront payment		$ 35.0
Clinical, regulatory and commercial milestone payments		193.0
Upfront payment received	$ 35.0	35.0
Revenue from upfront upfront payment		34.9
Deferred upfront payment		$ 0.1
Weighted average incremental borrowing rate		1.26%
Right of use assets \| €			€ 9,227
Right of use lease liabilities \| €			€ 8,947	€ 4,791
Number of segment \| Segment		1
Software and License Agreements \| Bottom of Range
Disclosure Of Voluntary Change In Accounting Policy [Line Items]
Estimated useful lives of software and license agreements		1 year
Software and License Agreements \| Top of Range
Disclosure Of Voluntary Change In Accounting Policy [Line Items]
Estimated useful lives of software and license agreements		8 years