v3.25.4
Post-employment benefits - Sensitivity of key assumptions (Detail) - EUR (€)
€ in Millions
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Post-employment benefits [Line Items]    
Percentage of reasonably possible decrease in actuarial assumption 1.00%  
Bottom of range    
Post-employment benefits [Line Items]    
Increase in actuarial assumption of life expectancy after retirement 6 months  
Top of range    
Post-employment benefits [Line Items]    
Increase in actuarial assumption of life expectancy after retirement 1 year  
Discount rate (1% movement)    
Post-employment benefits [Line Items]    
Increase € (80) € (123)
Decrease 98 150
Pension increase (1% movement)    
Post-employment benefits [Line Items]    
Increase 54 60
Decrease (47) (52)
Salary increase (1% movement)    
Post-employment benefits [Line Items]    
Increase 12 14
Decrease (11) (12)
Longevity    
Post-employment benefits [Line Items]    
Increase 26 34
Decrease € (21) € (24)
Percentage of reasonably possible decrease in actuarial assumption 10.00%