v3.26.1
Related parties - Additional Information (Detail)
€ in Millions
12 Months Ended
Dec. 31, 2025
EUR (€)
shares
Dec. 31, 2024
EUR (€)
shares
Dec. 31, 2023
EUR (€)
shares
Disclosure of transactions between related parties [line items]      
Description of transactions with related party There were no transactions with other related parties in 2025, nor in 2023 or 2024, which would require disclosure.    
Directors remuneration paid € 1 € 1 € 1
Outstanding share based payment instruments key management | shares 2,860,130 2,542,423 3,868,807
State of luxembourg [member]      
Disclosure of transactions between related parties [line items]      
Shareholder voting rights percentage 10.83    
Revenue € 32 € 31 € 27
Trade receivable € 0 € 0 € 4
Banque et Caisse d'Epargne de l'Etat [member]      
Disclosure of transactions between related parties [line items]      
Shareholder voting rights percentage 10.18    
Société Nationale de Crédit et d'Investissement [member]      
Disclosure of transactions between related parties [line items]      
Shareholder voting rights percentage 10.18