v3.26.1
Risk management - Schedule of weights used for current political and economic positions, by entity (Details)
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Pessimistic scenario 3 | Santander UK plc      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 20.00% 20.00%
Pessimistic scenario 2 | Santander UK plc      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 10.00% 10.00% 10.00%
Pessimistic scenario 2 | Santander Bank, National Association | US | Total North America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 18.00% 18.00% 18.00%
Pessimistic scenario 2 | Santander Consumer USA Holdings Inc. | US | Total North America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 18.00% 18.00% 18.00%
Pessimistic scenario 1 | Santander UK plc      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 25.00% 25.00% 10.00%
Pessimistic scenario 1 | Santander Bank, National Association | US | Total North America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 20.00% 20.00% 20.00%
Pessimistic scenario 1 | Santander Consumer USA Holdings Inc. | US | Total North America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 20.00% 20.00% 20.00%
Base scenario | Spain      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 40.00% 40.00% 40.00%
Base scenario | Santander UK plc      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 50.00% 50.00% 50.00%
Base scenario | Santander Bank, National Association | US | Total North America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 33.00% 33.00% 33.00%
Base scenario | Santander Consumer USA Holdings Inc. | US | Total North America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 33.00% 33.00% 33.00%
Base scenario | Banco Santander (Brasil) S.A. | Brazil | Total South America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 75.00% 75.00% 80.00%
Optimistic scenario  | Santander UK plc      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 15.00% 15.00% 10.00%
Optimistic scenario  | Santander Bank, National Association | US | Total North America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 30.00% 30.00% 30.00%
Optimistic scenario  | Santander Consumer USA Holdings Inc. | US | Total North America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 30.00% 30.00% 30.00%
Optimistic scenario  | Banco Santander (Brasil) S.A. | Brazil | Total South America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 13.00% 13.00% 10.00%
Pessimistic scenario  | Spain      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 30.00% 30.00% 30.00%
Pessimistic scenario  | Banco Santander (Brasil) S.A. | Brazil | Total South America      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 13.00% 13.00% 10.00%
Optimistic scenario 1 | Spain      
Disclosure of credit risk exposure [line items]      
Percentage of weightings associated with the macroeconomic scenarios 30.00% 30.00% 30.00%