v3.26.1
Financial Risks - Schedule of Credit Risk Concentration - Mortgage Loans (Detail) - Mortgage loans [member] - Credit risk [member] - EUR (€)
€ in Millions
Dec. 31, 2025
Dec. 31, 2024
Disclosure of credit risk exposure [line items]    
Credit risk concentrations € 9,754 € 10,680
Past due and impaired [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations (33) (118)
Agricultural mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 40 47
Agricultural mortgage loans [member] | Past due and impaired [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations (1)  
Apartment mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 4,954 5,618
Apartment mortgage loans [member] | Past due and impaired [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations (5) (8)
Industrial mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 455 474
Office mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 1,105 1,270
Office mortgage loans [member] | Past due and impaired [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations (27) (109)
Retail mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 1,257 1,384
Retail mortgage loans [member] | Past due and impaired [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 0 (1)
Other commercial mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 1,943 1,886
Americas [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 9,753 10,679
Americas [member] | Agricultural mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 40 47
Americas [member] | Apartment mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 4,954 5,618
Americas [member] | Industrial mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 455 474
Americas [member] | Office mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 1,105 1,270
Americas [member] | Retail mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 1,257 1,384
Americas [member] | Other commercial mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 1,942 1,885
International [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations 1 1
International [member] | Other commercial mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Credit risk concentrations € 1 € 1