v3.26.1
Defined Benefit Plans - Summary of Amounts Recognized in Statement of Financial Positions (Detail) - EUR (€)
€ in Millions
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of net defined benefit liability (asset) [Line Items]      
Present value of wholly or partly funded obligations € 2,852 € 3,140  
Fair value of plan assets (2,845) (3,123)  
Fair value of reimbursement rights (28) (9)  
Surplus Deficit In Plan (22) 7  
Present value of wholly unfunded obligations 406 450  
Ending Balance 384 457 € 546
Retirement Benefit Plans [member]      
Disclosure of net defined benefit liability (asset) [Line Items]      
Present value of wholly or partly funded obligations 2,852 3,140  
Fair value of plan assets (2,845) (3,123)  
Fair value of reimbursement rights (28) (9)  
Surplus Deficit In Plan (22) 7  
Present value of wholly unfunded obligations 239 262  
Ending Balance 217 269 368
Other Post Employment Benefit Plans [member]      
Disclosure of net defined benefit liability (asset) [Line Items]      
Present value of wholly or partly funded obligations 0 0  
Fair value of plan assets 0 0  
Fair value of reimbursement rights 0 0  
Surplus Deficit In Plan 0 0  
Present value of wholly unfunded obligations 167 189  
Ending Balance € 167 € 189 € 178