v3.26.1
Risk management - Schedule of evolution projection based on main macroeconomic indicators, by entity (Details)
 12 Months Ended
Dec. 31, 2025
Santander UK plc  
Disclosure of credit risk exposure [line items]  
Evolution projection period 5 years
Santander UK plc | Pessimistic scenario 2  
Disclosure of credit risk exposure [line items]  
Interest rate 2.40%
Unemployment rate 7.30%
Housing price change (2.90%)
GDP growth (0.02%)
Santander UK plc | Pessimistic scenario 1  
Disclosure of credit risk exposure [line items]  
Interest rate 3.50%
Unemployment rate 5.80%
Housing price change (0.20%)
GDP growth 0.20%
Santander UK plc | Base scenario  
Disclosure of credit risk exposure [line items]  
Interest rate 3.30%
Unemployment rate 4.50%
Housing price change 2.90%
GDP growth 1.40%
Santander UK plc | Optimistic scenario   
Disclosure of credit risk exposure [line items]  
Interest rate 3.00%
Unemployment rate 4.20%
Housing price change 4.40%
GDP growth 2.40%
Spain  
Disclosure of credit risk exposure [line items]  
Evolution projection period 5 years
Spain | Pessimistic scenario   
Disclosure of credit risk exposure [line items]  
Interest rate 2.70%
Unemployment rate 12.10%
Housing price change 3.30%
GDP growth 0.20%
Spain | Base scenario  
Disclosure of credit risk exposure [line items]  
Interest rate 2.50%
Unemployment rate 9.70%
Housing price change 4.10%
GDP growth 1.60%
Spain | Optimistic scenario   
Disclosure of credit risk exposure [line items]  
Interest rate 2.30%
Unemployment rate 8.20%
Housing price change 4.70%
GDP growth 2.40%
US | Santander Bank, National Association | Total North America  
Disclosure of credit risk exposure [line items]  
Evolution projection period 5 years
US | Santander Bank, National Association | Pessimistic scenario 2 | Total North America  
Disclosure of credit risk exposure [line items]  
Interest rate 1.80%
Unemployment rate 6.40%
Housing price change 0.20%
GDP growth 1.70%
Manheim growth (0.60%)
US | Santander Bank, National Association | Pessimistic scenario 1 | Total North America  
Disclosure of credit risk exposure [line items]  
Interest rate 2.60%
Unemployment rate 5.00%
Housing price change 0.70%
GDP growth 1.90%
Manheim growth (0.10%)
US | Santander Bank, National Association | Base scenario | Total North America  
Disclosure of credit risk exposure [line items]  
Interest rate 3.20%
Unemployment rate 4.20%
Housing price change 1.30%
GDP growth 2.00%
Manheim growth 0.30%
US | Santander Bank, National Association | Optimistic scenario  | Total North America  
Disclosure of credit risk exposure [line items]  
Interest rate 3.00%
Unemployment rate 3.70%
Housing price change 2.10%
GDP growth 2.70%
Manheim growth 0.10%
US | Santander Consumer USA Holdings Inc. | Total North America  
Disclosure of credit risk exposure [line items]  
Evolution projection period 5 years
US | Santander Consumer USA Holdings Inc. | Pessimistic scenario 2 | Total North America  
Disclosure of credit risk exposure [line items]  
Interest rate 1.80%
Unemployment rate 6.40%
Housing price change 0.20%
GDP growth 1.70%
Manheim index (0.60%)
US | Santander Consumer USA Holdings Inc. | Pessimistic scenario 1 | Total North America  
Disclosure of credit risk exposure [line items]  
Interest rate 2.60%
Unemployment rate 5.00%
Housing price change 0.70%
GDP growth 1.90%
Manheim index (0.10%)
US | Santander Consumer USA Holdings Inc. | Base scenario | Total North America  
Disclosure of credit risk exposure [line items]  
Interest rate 3.20%
Unemployment rate 4.20%
Housing price change 1.30%
GDP growth 2.00%
Manheim index 0.30%
US | Santander Consumer USA Holdings Inc. | Optimistic scenario  | Total North America  
Disclosure of credit risk exposure [line items]  
Interest rate 3.00%
Unemployment rate 3.70%
Housing price change 2.10%
GDP growth 2.70%
Manheim index 0.10%
Brazil | Total South America  
Disclosure of credit risk exposure [line items]  
Evolution projection period 5 years
Brazil | Banco Santander (Brasil) S.A. | Pessimistic scenario  | Total South America  
Disclosure of credit risk exposure [line items]  
Interest rate 11.50%
Unemployment rate 8.00%
Housing price change 1.10%
GDP growth (0.20%)
Burden income 27.00%
Brazil | Banco Santander (Brasil) S.A. | Base scenario | Total South America  
Disclosure of credit risk exposure [line items]  
Interest rate 10.90%
Unemployment rate 6.50%
Housing price change 5.90%
GDP growth 1.90%
Burden income 26.80%
Brazil | Banco Santander (Brasil) S.A. | Optimistic scenario  | Total South America  
Disclosure of credit risk exposure [line items]  
Interest rate 10.30%
Unemployment rate 5.40%
Housing price change 10.30%
GDP growth 3.80%
Burden income 26.10%