v3.26.1
Property, plant and equipment - Additional Information (Details) - EUR (€)
€ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Right of use – Buildings | Gross book value of tangible assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Increase in right-of-use assets € 132 € 228
Transfer € 0 0
Right of use – Buildings | Bottom of Range    
Disclosure of detailed information about property, plant and equipment [line items]    
Depreciation periods of property, plant and equipment 5 years  
Right of use – Buildings | Top of Range    
Disclosure of detailed information about property, plant and equipment [line items]    
Depreciation periods of property, plant and equipment 10 years  
Technical equipment | Gross book value of tangible assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Increase in right-of-use assets € 78 166
Transfer € 26 0
Technical equipment | Bottom of Range    
Disclosure of detailed information about property, plant and equipment [line items]    
Depreciation periods of property, plant and equipment 3 years  
Technical equipment | Top of Range    
Disclosure of detailed information about property, plant and equipment [line items]    
Depreciation periods of property, plant and equipment 10 years  
Office and IT equipment | Gross book value of tangible assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Increase in right-of-use assets € 76 227
Transfer € 10 (15)
Office and IT equipment | Bottom of Range    
Disclosure of detailed information about property, plant and equipment [line items]    
Depreciation periods of property, plant and equipment 1 year  
Office and IT equipment | Top of Range    
Disclosure of detailed information about property, plant and equipment [line items]    
Depreciation periods of property, plant and equipment 10 years  
Fixtures, fittings and installations | Gross book value of tangible assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Increase in right-of-use assets € 86 48
Transfer € 8 22
Fixtures, fittings and installations | Bottom of Range    
Disclosure of detailed information about property, plant and equipment [line items]    
Depreciation periods of property, plant and equipment 5 years  
Fixtures, fittings and installations | Top of Range    
Disclosure of detailed information about property, plant and equipment [line items]    
Depreciation periods of property, plant and equipment 10 years  
Transfer € 0 0
Gross book value of tangible assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Increase in right-of-use assets 670 903
Transfer € 0 (25)
Right-of-use assets [member] | Gross book value of tangible assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Increase in right-of-use assets   200
Right-of-use assets [member] | Gross book value of tangible assets | Wattignies    
Disclosure of detailed information about property, plant and equipment [line items]    
Increase in right-of-use assets   100
Right-of-use assets [member] | Gross book value of tangible assets | Waccano    
Disclosure of detailed information about property, plant and equipment [line items]    
Increase in right-of-use assets   € 100