v3.26.1
Financial Risks - Summary of Credit Risk Exposure - Debt Securities (Detail) - Financial assets measured at FVOCI - with recycling [member] - EUR (€)
€ in Millions
Dec. 31, 2025
Dec. 31, 2024
Gross carrying amount [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI € 49,747 € 54,677
Gross carrying amount [member] | AAA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 3,843 3,295
Gross carrying amount [member] | AA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 7,788 9,101
Gross carrying amount [member] | A [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 18,403 19,443
Gross carrying amount [member] | BBB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 18,135 20,732
Gross carrying amount [member] | BB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 934 1,106
Gross carrying amount [member] | B [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 245 456
Gross carrying amount [member] | CCC and lower [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 398 544
Gross carrying amount [member] | Lifetime ECL not credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 358 337
Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | AAA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | AA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | A [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | BBB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 84 7
Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | BB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 124 157
Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | B [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 95 95
Gross carrying amount [member] | Lifetime ECL not credit impaired [member] | CCC and lower [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 55 79
Gross carrying amount [member] | Purchased credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 75 92
Gross carrying amount [member] | Purchased credit impaired [member] | AAA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Purchased credit impaired [member] | AA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Purchased credit impaired [member] | A [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Purchased credit impaired [member] | BBB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 1 1
Gross carrying amount [member] | Purchased credit impaired [member] | BB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Purchased credit impaired [member] | B [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Purchased credit impaired [member] | CCC and lower [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 74 91
Gross carrying amount [member] | 12-month ECL [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 49,082 53,957
Gross carrying amount [member] | 12-month ECL [member] | AAA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 3,843 3,295
Gross carrying amount [member] | 12-month ECL [member] | AA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 7,787 9,100
Gross carrying amount [member] | 12-month ECL [member] | A [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 18,394 19,443
Gross carrying amount [member] | 12-month ECL [member] | BBB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 18,050 20,724
Gross carrying amount [member] | 12-month ECL [member] | BB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 810 949
Gross carrying amount [member] | 12-month ECL [member] | B [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 150 361
Gross carrying amount [member] | 12-month ECL [member] | CCC and lower [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 48 85
Gross carrying amount [member] | Lifetime ECL credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 232 291
Gross carrying amount [member] | Lifetime ECL credit impaired [member] | AAA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Lifetime ECL credit impaired [member] | AA [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 1 1
Gross carrying amount [member] | Lifetime ECL credit impaired [member] | A [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 9  
Gross carrying amount [member] | Lifetime ECL credit impaired [member] | BBB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Lifetime ECL credit impaired [member] | BB [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Lifetime ECL credit impaired [member] | B [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 0  
Gross carrying amount [member] | Lifetime ECL credit impaired [member] | CCC and lower [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI 221 289
Expected credit loss [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI (347) (341)
Expected credit loss [member] | Lifetime ECL not credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI (27) (42)
Expected credit loss [member] | Purchased credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI (1) (4)
Expected credit loss [member] | 12-month ECL [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI (189) (187)
Expected credit loss [member] | Lifetime ECL credit impaired [member]    
Disclosure of credit risk exposure [line items]    
Financial assets measured at FVOCI € (130) € (108)