v3.26.1
Financial Risks - Summary of Credit Risk Exposure - Mortgages (Detail) - EUR (€)
€ in Millions
Dec. 31, 2025
Dec. 31, 2024
Disclosure of credit risk exposure [line items]    
Loans at amortized cost € 69,293 € 76,020
Mortgage loans [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 9,672 10,598
Mortgage loans [member] | Lifetime ECL not credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 94 60
Mortgage loans [member] | Purchased credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | 12-month ECL [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 9,575 10,535
Mortgage loans [member] | Lifetime ECL credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 2 2
Mortgage loans [member] | Gross carrying amount [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 9,705 10,716
Mortgage loans [member] | Gross carrying amount [member] | Internal grade 1 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 847 1,013
Mortgage loans [member] | Gross carrying amount [member] | Internal grade 2 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 4,023 4,421
Mortgage loans [member] | Gross carrying amount [member] | Internal grade 3 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 4,319 4,546
Mortgage loans [member] | Gross carrying amount [member] | Internal grade 4 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 423 654
Mortgage loans [member] | Gross carrying amount [member] | Internal grade 5 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 93 81
Mortgage loans [member] | Gross carrying amount [member] | Internal grade 6 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Internal grade 7 or lower [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL not credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 115 135
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | Internal grade 1 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0 35
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | Internal grade 2 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0 11
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | Internal grade 3 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 15  
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | Internal grade 4 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 7 10
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | Internal grade 5 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 93 78
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | Internal grade 6 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | Internal grade 7 or lower [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Purchased credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Purchased credit impaired [member] | Internal grade 1 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Purchased credit impaired [member] | Internal grade 2 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Purchased credit impaired [member] | Internal grade 3 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Purchased credit impaired [member] | Internal grade 4 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Purchased credit impaired [member] | Internal grade 5 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Purchased credit impaired [member] | Internal grade 6 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Purchased credit impaired [member] | Internal grade 7 or lower [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | 12-month ECL [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 9,587 10,573
Mortgage loans [member] | Gross carrying amount [member] | 12-month ECL [member] | Internal grade 1 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 847 977
Mortgage loans [member] | Gross carrying amount [member] | 12-month ECL [member] | Internal grade 2 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 4,023 4,410
Mortgage loans [member] | Gross carrying amount [member] | 12-month ECL [member] | Internal grade 3 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 4,304 4,539
Mortgage loans [member] | Gross carrying amount [member] | 12-month ECL [member] | Internal grade 4 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 413 644
Mortgage loans [member] | Gross carrying amount [member] | 12-month ECL [member] | Internal grade 5 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0 4
Mortgage loans [member] | Gross carrying amount [member] | 12-month ECL [member] | Internal grade 6 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | 12-month ECL [member] | Internal grade 7 or lower [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 3 7
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL credit impaired [member] | Internal grade 1 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL credit impaired [member] | Internal grade 2 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL credit impaired [member] | Internal grade 3 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0 7
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL credit impaired [member] | Internal grade 4 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 3  
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL credit impaired [member] | Internal grade 5 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL credit impaired [member] | Internal grade 6 [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Gross carrying amount [member] | Lifetime ECL credit impaired [member] | Internal grade 7 or lower [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Expected credit loss [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost (33) (118)
Mortgage loans [member] | Expected credit loss [member] | Lifetime ECL not credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost (21) (75)
Mortgage loans [member] | Expected credit loss [member] | Purchased credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost 0  
Mortgage loans [member] | Expected credit loss [member] | 12-month ECL [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost (11) (38)
Mortgage loans [member] | Expected credit loss [member] | Lifetime ECL credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Loans at amortized cost € (1) € (5)