v3.26.1
Other disclosures - Schedule of financial instruments at fair value whose measurement was based on internal models (Levels 2 and 3) (Details) - EUR (€)
€ in Millions
Jun. 30, 2026
Dec. 31, 2025
Jun. 30, 2025
Dec. 31, 2024
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value € 1,496 € 1,110    
Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 182,514 163,796    
Financial liabilities, at fair value 224,499 198,377    
Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 20,857 18,487 € 16,981 € 15,319
Financial liabilities, at fair value 1,496 1,110 1,216 1,352
Financial liabilities held for trading | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 1,120 864 954 934
Financial liabilities held for trading | Derivatives | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 922 864 876 934
Financial liabilities held for trading | Swaps | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 431 418 499 479
Financial liabilities held for trading | Exchange rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 17 34 15 0
Financial liabilities held for trading | Interest rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 84 95 111 79
Financial liabilities held for trading | Index and securities options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 188 151 155 294
Financial liabilities held for trading | Other | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 199 166 67 82
Financial liabilities designated at fair value through profit or loss | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 128 0 0 160
Liabilities under insurance contracts | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 244 227 232 246
Financial assets held for trading | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 7,816 6,496 5,477 3,930
Financial assets held for trading | Equity instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value     0 0
Financial assets held for trading | Derivatives | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 976 971 885 947
Financial assets held for trading | Swaps | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 546 551 649 556
Financial assets held for trading | Exchange rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 31 39 15 2
Financial assets held for trading | Interest rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 1 39 42 30
Financial assets held for trading | Interest rate futures | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value     2 0
Financial assets held for trading | Index and securities options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 214 120 56 241
Financial assets held for trading | Other | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 181 222 121 118
Financial assets held for trading | Debt instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 311 340 212 413
Non-trading financial assets mandatorily at fair value through profit or loss | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 2,998 2,889 2,359 2,588
Non-trading financial assets mandatorily at fair value through profit or loss | Equity instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 2,603 2,543 2,045 1,841
Non-trading financial assets mandatorily at fair value through profit or loss | Debt instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 230 175 232 242
Financial assets designated at fair value through profit or loss | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 51 34 45 106
Financial assets designated at fair value through profit or loss | Debt instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 24 20 28 86
Financial assets at fair value through other comprehensive income | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 9,992 9,061 9,086 8,675
Financial assets at fair value through other comprehensive income | Equity instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 273 272 286 375
Financial assets at fair value through other comprehensive income | Debt instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 1,005 887 € 1,271 € 1,047
Financial assets and liabilities, category | Financial liabilities held for trading | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 157,680 133,490    
Financial assets and liabilities, category | Financial liabilities held for trading | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 1,120 864    
Financial assets and liabilities, category | Financial liabilities held for trading | Deposits | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 98,944 75,563    
Financial assets and liabilities, category | Financial liabilities held for trading | Deposits | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 198 0    
Financial assets and liabilities, category | Financial liabilities held for trading | Derivatives | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 49,841 50,248    
Financial assets and liabilities, category | Financial liabilities held for trading | Derivatives | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 922 864    
Financial assets and liabilities, category | Financial liabilities held for trading | Swaps | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 35,089 33,597    
Financial assets and liabilities, category | Financial liabilities held for trading | Swaps | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 431 418    
Financial assets and liabilities, category | Financial liabilities held for trading | Exchange rate options | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 828 903    
Financial assets and liabilities, category | Financial liabilities held for trading | Exchange rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 17 34    
Financial assets and liabilities, category | Financial liabilities held for trading | Interest rate options | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 1,853 1,951    
Financial assets and liabilities, category | Financial liabilities held for trading | Interest rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 84 95    
Financial assets and liabilities, category | Financial liabilities held for trading | Index and securities options | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 2,352 1,094    
Financial assets and liabilities, category | Financial liabilities held for trading | Index and securities options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 188 151    
Financial assets and liabilities, category | Financial liabilities held for trading | Interest rate and equity futures | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 520 121    
Financial assets and liabilities, category | Financial liabilities held for trading | Interest rate and equity futures | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 3 0    
Financial assets and liabilities, category | Financial liabilities held for trading | Other | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 9,199 12,582    
Financial assets and liabilities, category | Financial liabilities held for trading | Other | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 199 166    
Financial assets and liabilities, category | Financial liabilities held for trading | Short Positions | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 8,895 7,679    
Financial assets and liabilities, category | Financial liabilities held for trading | Short Positions | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 0 0    
Financial assets and liabilities, category | Hedging derivatives | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 4,490 4,229    
Financial assets and liabilities, category | Hedging derivatives | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 4 19    
Financial assets and liabilities, category | Hedging derivatives | Swaps | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 3,861 4,191    
Financial assets and liabilities, category | Hedging derivatives | Swaps | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 4 19    
Financial assets and liabilities, category | Hedging derivatives | Interest rate options | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 0 0    
Financial assets and liabilities, category | Hedging derivatives | Interest rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 0 0    
Financial assets and liabilities, category | Hedging derivatives | Other | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 629 38    
Financial assets and liabilities, category | Hedging derivatives | Other | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 0 0    
Financial assets and liabilities, category | Financial liabilities designated at fair value through profit or loss | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 43,279 42,148    
Financial assets and liabilities, category | Financial liabilities designated at fair value through profit or loss | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 128 0    
Financial assets and liabilities, category | Liabilities under insurance contracts | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 19,103 18,510    
Financial assets and liabilities, category | Liabilities under insurance contracts | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial liabilities, at fair value 244 227    
Financial assets and liabilities, category | Financial assets held for trading | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 158,735 139,293    
Financial assets and liabilities, category | Financial assets held for trading | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 7,816 6,496    
Financial assets and liabilities, category | Financial assets held for trading | Loans and receivables | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 84,231 67,992    
Financial assets and liabilities, category | Financial assets held for trading | Loans and receivables | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 6,529 5,185    
Financial assets and liabilities, category | Financial assets held for trading | Debt instruments | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 17,133 14,456    
Financial assets and liabilities, category | Financial assets held for trading | Debt instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 311 340    
Financial assets and liabilities, category | Financial assets held for trading | Equity instruments | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 16 14    
Financial assets and liabilities, category | Financial assets held for trading | Equity instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 0 0    
Financial assets and liabilities, category | Financial assets held for trading | Derivatives | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 57,355 56,831    
Financial assets and liabilities, category | Financial assets held for trading | Derivatives | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 976 971    
Financial assets and liabilities, category | Financial assets held for trading | Swaps | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 42,279 39,716    
Financial assets and liabilities, category | Financial assets held for trading | Swaps | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 546 551    
Financial assets and liabilities, category | Financial assets held for trading | Exchange rate options | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 1,160 1,332    
Financial assets and liabilities, category | Financial assets held for trading | Exchange rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 31 39    
Financial assets and liabilities, category | Financial assets held for trading | Interest rate options | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 1,824 1,490    
Financial assets and liabilities, category | Financial assets held for trading | Interest rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 1 39    
Financial assets and liabilities, category | Financial assets held for trading | Interest rate futures | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 774 177    
Financial assets and liabilities, category | Financial assets held for trading | Interest rate futures | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 3 0    
Financial assets and liabilities, category | Financial assets held for trading | Index and securities options | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 552 439    
Financial assets and liabilities, category | Financial assets held for trading | Index and securities options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 214 120    
Financial assets and liabilities, category | Financial assets held for trading | Other | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 10,766 13,677    
Financial assets and liabilities, category | Financial assets held for trading | Other | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 181 222    
Financial assets and liabilities, category | Hedging derivatives | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 5,006 3,924    
Financial assets and liabilities, category | Hedging derivatives | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 0 7    
Financial assets and liabilities, category | Hedging derivatives | Swaps | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 4,736 3,690    
Financial assets and liabilities, category | Hedging derivatives | Swaps | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 0 7    
Financial assets and liabilities, category | Hedging derivatives | Interest rate options | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 102 91    
Financial assets and liabilities, category | Hedging derivatives | Interest rate options | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 0 0    
Financial assets and liabilities, category | Hedging derivatives | Other | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 168 143    
Financial assets and liabilities, category | Hedging derivatives | Other | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 0 0    
Financial assets and liabilities, category | Non-trading financial assets mandatorily at fair value through profit or loss | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 2,413 2,465    
Financial assets and liabilities, category | Non-trading financial assets mandatorily at fair value through profit or loss | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 2,998 2,889    
Financial assets and liabilities, category | Non-trading financial assets mandatorily at fair value through profit or loss | Loans and receivables | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 1,368 1,512    
Financial assets and liabilities, category | Non-trading financial assets mandatorily at fair value through profit or loss | Loans and receivables | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 165 171    
Financial assets and liabilities, category | Non-trading financial assets mandatorily at fair value through profit or loss | Equity instruments | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 1,028 899    
Financial assets and liabilities, category | Non-trading financial assets mandatorily at fair value through profit or loss | Equity instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 2,603 2,543    
Financial assets and liabilities, category | Non-trading financial assets mandatorily at fair value through profit or loss | Debt instruments | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 17 54    
Financial assets and liabilities, category | Non-trading financial assets mandatorily at fair value through profit or loss | Debt instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 230 175    
Financial assets and liabilities, category | Financial assets designated at fair value through profit or loss | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 4,976 5,152    
Financial assets and liabilities, category | Financial assets designated at fair value through profit or loss | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 51 34    
Financial assets and liabilities, category | Financial assets designated at fair value through profit or loss | Loans and receivables | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 4,963 5,138    
Financial assets and liabilities, category | Financial assets designated at fair value through profit or loss | Loans and receivables | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 27 14    
Financial assets and liabilities, category | Financial assets designated at fair value through profit or loss | Debt instruments | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 13 14    
Financial assets and liabilities, category | Financial assets designated at fair value through profit or loss | Debt instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 24 20    
Financial assets and liabilities, category | Financial assets at fair value through other comprehensive income | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 11,384 12,962    
Financial assets and liabilities, category | Financial assets at fair value through other comprehensive income | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 9,992 9,061    
Financial assets and liabilities, category | Financial assets at fair value through other comprehensive income | Loans and receivables | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 4,085 6,124    
Financial assets and liabilities, category | Financial assets at fair value through other comprehensive income | Loans and receivables | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 8,714 7,902    
Financial assets and liabilities, category | Financial assets at fair value through other comprehensive income | Debt instruments | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 7,296 6,819    
Financial assets and liabilities, category | Financial assets at fair value through other comprehensive income | Debt instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 1,005 887    
Financial assets and liabilities, category | Financial assets at fair value through other comprehensive income | Equity instruments | Level 2        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value 3 19    
Financial assets and liabilities, category | Financial assets at fair value through other comprehensive income | Equity instruments | Level 3        
Measurement of financial assets and liabilities and recognition of fair value changes        
Financial assets, at fair value € 273 € 272