v3.25.1
Segment information - Non-current assets by location (Details) - EUR (€)
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Disclosure of geographical areas [line items]      
Non-current assets € 796,269,000 € 495,807,000  
Property, Plant and Equipment, Intangible Assets and Goodwill      
Disclosure of geographical areas [line items]      
Non-current assets 357,770,000 323,784,000 € 370,420,000
Property, Plant and Equipment, Intangible Assets and Goodwill | Belgium      
Disclosure of geographical areas [line items]      
Non-current assets 95,686,000 56,209,000 72,087,000
Property, Plant and Equipment, Intangible Assets and Goodwill | France      
Disclosure of geographical areas [line items]      
Non-current assets 5,000 1,438,000 20,397,000
Property, Plant and Equipment, Intangible Assets and Goodwill | The Netherlands      
Disclosure of geographical areas [line items]      
Non-current assets 239,454,000 251,230,000 255,461,000
Property, Plant and Equipment, Intangible Assets and Goodwill | Switzerland      
Disclosure of geographical areas [line items]      
Non-current assets 92,000 3,247,000 4,962,000
Property, Plant and Equipment, Intangible Assets and Goodwill | Spain      
Disclosure of geographical areas [line items]      
Non-current assets     3,037,000
Property, Plant and Equipment, Intangible Assets and Goodwill | United States of America      
Disclosure of geographical areas [line items]      
Non-current assets € 22,533,000 € 11,660,000 12,729,000
Property, Plant and Equipment, Intangible Assets and Goodwill | Other Countries      
Disclosure of geographical areas [line items]      
Non-current assets     € 1,747,000