v3.26.1
Defined Benefit Plans - Summary of Breakdown of Plan Assets for Retirement of Benefit Plans (Detail) - EUR (€)
€ in Millions
Dec. 31, 2025
Dec. 31, 2024
Disclosure of fair value of plan assets [Line Items]    
Debt instrument € 900 € 869
Derivatives (30) (183)
Investment funds 1,625 2,027
Other 350 410
On December 31 € 2,845 € 3,123
Debt instrument 32.00% 28.00%
Derivatives (1.00%) (6.00%)
Investment funds 57.00% 65.00%
Other 12.00% 13.00%
On December 31 100.00% 100.00%
Quoted Plan Assets [member]    
Disclosure of fair value of plan assets [Line Items]    
Debt instrument € 702 € 594
Derivatives 0 0
Investment funds 0 0
Other 0 0
On December 31 702 594
Unquoted plan assets [member]    
Disclosure of fair value of plan assets [Line Items]    
Debt instrument 198 275
Derivatives (30) (183)
Investment funds 1,625 2,027
Other 350 410
On December 31 € 2,144 € 2,529