v3.26.3
Nature of the business and principles and accounting methods (Details)
€ in Millions, $ in Millions
1 Months Ended 3 Months Ended 9 Months Ended
Sep. 29, 2026
USD ($)
Aug. 03, 2026
USD ($)
Jul. 08, 2026
USD ($)
Mar. 17, 2026
Apr. 07, 2025
USD ($)
Apr. 07, 2025
EUR (€)
Jan. 31, 2026
USD ($)
Jan. 31, 2026
EUR (€)
Dec. 31, 2025
USD ($)
Dec. 31, 2025
EUR (€)
Sep. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Dec. 16, 2025
USD ($)
Dec. 16, 2025
EUR (€)
Subsidiary or Equity Method Investee [Line Items]                            
Net cash used in operating and investing activities                     $ (159.4) $ (86.7)    
Cash and cash equivalents                 $ 194.2   165.7      
Prepaid right-of-use-asset                 3.9   $ 7.4      
Fareva La Vallée                            
Subsidiary or Equity Method Investee [Line Items]                            
Foreign currency exchange rate, remeasurement                     1.14      
Manufacturing and supply agreement, contractual period       8 years                    
Manufacturing and supply agreement, contractual period, renewal option       2 years                    
Purchase commitment, remaining minimum amount committed                     $ 0.6      
Peanut Source Material Agreement, Fareva La Vallée                            
Subsidiary or Equity Method Investee [Line Items]                            
Foreign currency exchange rate, remeasurement                     1.14      
Prepaid right-of-use-asset                     $ 4.1      
Peanut Drug Substance Agreement, Fareva La Vallée                            
Subsidiary or Equity Method Investee [Line Items]                            
Foreign currency exchange rate, remeasurement     1.14                      
Prepaid right-of-use-asset                     $ 3.3      
Services fees funded     $ 3.3                      
Peanut Drug Substance Agreement, Fareva La Vallée | Maximum                            
Subsidiary or Equity Method Investee [Line Items]                            
Service fee     3.9                      
Transfer service fee     $ 3.2                      
American Depositary Share                            
Subsidiary or Equity Method Investee [Line Items]                            
Proceeds from issuance of common stock $ 50.0 $ 50.0                        
Private investment in Public Equity                            
Subsidiary or Equity Method Investee [Line Items]                            
Proceeds from issuance of common stock         $ 125.5 € 116.3 $ 94.7 € 81.0 $ 100.7 € 85.7        
Issuance of common stock, additional amount                         $ 195.4 € 166.7
Foreign currency exchange rate, remeasurement                         1.17 1.17