Property, plant and equipment - Disclosure of reconciliation of property, plant and equipment (Details) - EUR (€) € in Thousands	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	€ 2,090
Property, plant and equipment including right-of-use assets at end of period	1,783	€ 2,666
ROU
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	1,563
Property, plant and equipment including right-of-use assets at end of period	1,286	1,950
BUILDINGS
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	1,706
Property, plant and equipment including right-of-use assets at end of period	1,395	2,205
EQUIPMENT
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	59
Property, plant and equipment including right-of-use assets at end of period	62	94
FURNITURE AND COMPUTER EQUIPMENT
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	325
Property, plant and equipment including right-of-use assets at end of period	326	366
GROSS VALUES \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	4,274	4,029
Acquisition	55	25
Disposal		(34)
Effect of the change in foreign currency exchange rates	11	(20)
Property, plant and equipment including right-of-use assets at end of period	4,340	4,000
GROSS VALUES \| ROU
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	2,865	2,526
Acquisition	0	0
Disposal		0
Effect of the change in foreign currency exchange rates	8	(21)
Property, plant and equipment including right-of-use assets at end of period	2,874	2,505
GROSS VALUES \| BUILDINGS \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	3,204	2,818
Acquisition	0	0
Disposal		0
Effect of the change in foreign currency exchange rates	8	(4)
Property, plant and equipment including right-of-use assets at end of period	3,212	2,814
GROSS VALUES \| EQUIPMENT \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	463	513
Acquisition	11	0
Disposal		(29)
Effect of the change in foreign currency exchange rates	0	0
Property, plant and equipment including right-of-use assets at end of period	474	484
GROSS VALUES \| FURNITURE AND COMPUTER EQUIPMENT \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	607	698
Acquisition	44	25
Disposal		(5)
Effect of the change in foreign currency exchange rates	3	(16)
Property, plant and equipment including right-of-use assets at end of period	654	702
DEPRECIATION \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(2,184)	(1,363)
Disposal		34
Effect of the change in foreign currency exchange rates	(4)	6
Increase	(369)	(266)
Property, plant and equipment including right-of-use assets at end of period	(2,558)	(1,590)
DEPRECIATION \| ROU
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(1,302)	(575)
Disposal		0
Effect of the change in foreign currency exchange rates	(6)	2
Increase	(280)	(194)
Property, plant and equipment including right-of-use assets at end of period	(1,587)	(767)
DEPRECIATION \| BUILDINGS \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(1,498)	(613)
Disposal		0
Effect of the change in foreign currency exchange rates	(6)	1
Increase	(314)	(224)
Property, plant and equipment including right-of-use assets at end of period	(1,818)	(836)
DEPRECIATION \| EQUIPMENT \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(404)	(419)
Disposal		29
Effect of the change in foreign currency exchange rates	0	0
Increase	(8)	(8)
Property, plant and equipment including right-of-use assets at end of period	(412)	(398)
DEPRECIATION \| FURNITURE AND COMPUTER EQUIPMENT \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(281)	(332)
Disposal		5
Effect of the change in foreign currency exchange rates	1	5
Increase	(48)	(34)
Property, plant and equipment including right-of-use assets at end of period	€ (328)	€ (356)

The amount of additions to property, plant and equipment including right-of-use assets other than those acquired through business combinations. [Refer: Total for all business combinations [member]; Property, plant and equipment including right-of-use assets]

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- References

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- Definition

The decrease in property, plant and equipment including right-of-use assets resulting from disposals. [Refer: Property, plant and equipment including right-of-use assets]

+ References

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- Definition

The increase (decrease) in property, plant and equipment including right-of-use assets resulting from net exchange differences arising on the translation of the financial statements from the functional currency into a different presentation currency, including the translation of a foreign operation into the presentation currency of the reporting entity. [Refer: Property, plant and equipment including right-of-use assets]

+ References

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- Definition

The amount of property, plant and equipment including right-of-use assets whose underlying assets would be presented as property, plant and equipment if they were owned. [Refer: Property, plant and equipment; Right-of-use assets]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2025-01-01
-Paragraph 47
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-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
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-URIDate 2025-03-27

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- References

No definition available.

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