v3.25.4
Derivatives and hedge accounting - Maturity derivatives designated in fair value hedging (Details) - -  fair value hedges - Net payer and receiver swap - EUR (€)
€ in Millions
Dec. 31, 2025
Dec. 31, 2024
– Interest rate swaps | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument € 39,279 € 50,358
– Interest rate swaps | Less than 1 month | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument 1,994 43
– Interest rate swaps | 1 to 3 months | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument 4,453 1,224
– Interest rate swaps | 3 to 12 months | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument 7,778 7,341
– Interest rate swaps | 1 to 2 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument 6,726 14,134
– Interest rate swaps | 2 to 3 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument 12,149 6,313
– Interest rate swaps | 3 to 4 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument 8,484 12,050
– Interest rate swaps | 4 to 5 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument 4,694 7,688
– Interest rate swaps | >5 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument (6,999) 1,564
– Other interest derivatives | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument (2,780) (2,540)
– Other interest derivatives | Less than 1 month | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument (3) (4)
– Other interest derivatives | 1 to 3 months | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument (31) (47)
– Other interest derivatives | 3 to 12 months | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument (211) (218)
– Other interest derivatives | 1 to 2 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument (348) (317)
– Other interest derivatives | 2 to 3 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument (457) (389)
– Other interest derivatives | 3 to 4 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument (297) (347)
– Other interest derivatives | 4 to 5 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument (274) (287)
– Other interest derivatives | >5 years | Interest rate risk    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument € (1,157) (932)
– Cross currency swaps | Foreign exchange    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument   (299)
– Cross currency swaps | Less than 1 month | Foreign exchange    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument   (142)
– Cross currency swaps | 1 to 3 months | Foreign exchange    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument   (60)
– Cross currency swaps | 3 to 12 months | Foreign exchange    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument   (98)
– Cross currency swaps | 1 to 2 years | Foreign exchange    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument  
– Cross currency swaps | 2 to 3 years | Foreign exchange    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument  
– Cross currency swaps | 3 to 4 years | Foreign exchange    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument  
– Cross currency swaps | 4 to 5 years | Foreign exchange    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument  
– Cross currency swaps | >5 years | Foreign exchange    
Disclosure of detailed information about hedging instruments [line items]    
Nominal amount of hedging instrument