v3.26.1
Commitments and contingencies - Schedule of Arising Capital Expenditure Commitments (Detail) - EUR (€)
€ in Millions
Dec. 31, 2025
Dec. 31, 2024
Capital expenditure commitments [Member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Capital Commitments € 594 € 281
Capital expenditure commitments [Member] | Not later than one year [member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Capital Commitments 273 96
Capital expenditure commitments [Member] | Later than one year and not later than five years [member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Capital Commitments 279 143
Capital expenditure commitments [Member] | Later than five years [member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Capital Commitments 42 42
Contributions to Joint Ventures [Member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Contractual Capital Commitments 157  
Contributions to Joint Ventures [Member] | Not later than one year [member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Contractual Capital Commitments 23  
Contributions to Joint Ventures [Member] | Later than one year and not later than five years [member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Contractual Capital Commitments 58  
Contributions to Joint Ventures [Member] | Later than five years [member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Contractual Capital Commitments 76  
Other commitments [Member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Capital Commitments 783 335
Other commitments [Member] | Not later than one year [member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Capital Commitments 313 160
Other commitments [Member] | Later than one year and not later than five years [member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Capital Commitments 407 130
Other commitments [Member] | Later than five years [member]    
Schedule of Arising capital expenditure commitments [Line Items]    
Capital Commitments € 63 € 45