v3.26.1
Shareholders' equity - Additional Information (Detail)
€ / shares in Units, $ / shares in Units, $ in Millions
6 Months Ended
Mar. 12, 2026
EUR (€)
€ / shares
shares
Mar. 12, 2026
USD ($)
shares
Jun. 30, 2026
EUR (€)
€ / shares
shares
Jun. 30, 2025
EUR (€)
Mar. 12, 2026
$ / shares
Dec. 31, 2025
€ / shares
shares
Disclosure of classes of share capital [line items]            
Issue Of Share Capital Net Of Transaction Costs     € 21,152,000      
Public Offering [Member] | Major ordinary share transactions [member]            
Disclosure of classes of share capital [line items]            
Sale Of Stock Issue Price Per Share | $ / shares         $ 10.02  
At-the-Market Offering Program            
Disclosure of classes of share capital [line items]            
Gross Proceeds From Initial Public Offer € 21,600,000 $ 25.0        
Payments for share issue costs 500,000 $ 0.6        
Issued capital [Member]            
Disclosure of classes of share capital [line items]            
Issue Of Share Capital Net Of Transaction Costs     25,000      
Issued capital [Member] | At-the-Market Offering Program            
Disclosure of classes of share capital [line items]            
Issue Of Share Capital Net Of Transaction Costs 25,000          
Share premium [Member]            
Disclosure of classes of share capital [line items]            
Issue Of Share Capital Net Of Transaction Costs     € 21,127,000      
Share premium [Member] | At-the-Market Offering Program            
Disclosure of classes of share capital [line items]            
Issue Of Share Capital Net Of Transaction Costs € 21,100,000          
Leerink Partners Llc [Member] | At-the-Market Offering Program            
Disclosure of classes of share capital [line items]            
Increase (decrease) in number of ordinary shares issued | shares | shares 2,500,000 2,500,000        
Sale Of Stock Issue Price Per Share | € / shares € 8.68          
Reorganization [Member]            
Disclosure of classes of share capital [line items]            
Number of shares outstanding | shares     136,689,977     134,071,432
Par value per share | € / shares     € 0.01     € 0.01
Ordinary Shares [Member] | Issued capital [Member]            
Disclosure of classes of share capital [line items]            
Issue of equity     € 1,000 € 100    
Ordinary Shares [Member] | Share premium [Member]            
Disclosure of classes of share capital [line items]            
Issue of equity     € 600,000 € 8,600