v3.26.1
Accounting policies and statement of compliance - Additional Information (Details) - EUR (€)
 12 Months Ended 89 Months Ended
Mar. 24, 2016
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2025
Disclosure of initial application of standards or interpretations [Line Items]            
Defined contribution plan, contribution percentage   2.20%        
Defined contribution plan, contribution percentage by employer   1.40%        
Defined contribution plan, contribution percentage by employee   0.80%        
Other long term benefits, years of service, threshold one 10 years 10 years        
Other long term benefits, years of service, threshold two 15 years 15 years        
Other long term benefits, years of service, threshold three 20 years 20 years        
Income taxes refund, classified as operating activities   € 6,500,000 € 8,600,000 € 13,000,000    
Impairment of intangible assets   € 0 0 0    
PH5401 (anti-C5aR) rights acquired from Novo Nordisk A/S            
Disclosure of initial application of standards or interpretations [Line Items]            
Impairment of intangible assets         € 41,000,000 € 0
Other intangible assets            
Disclosure of initial application of standards or interpretations [Line Items]            
Impairment of intangible assets     € 0 € 0    
Other intangible assets | Bottom of range            
Disclosure of initial application of standards or interpretations [Line Items]            
Amortisation period, intangible assets other than goodwill   1 year        
Other intangible assets | Top of range            
Disclosure of initial application of standards or interpretations [Line Items]            
Amortisation period, intangible assets other than goodwill   3 years