v3.26.1
Provisions - Non-tax-related proceedings (Details)
€ in Thousands, £ in Millions, zł in Millions
5 Months Ended 6 Months Ended 12 Months Ended 19 Months Ended
Mar. 30, 2026
EUR (€)
Mar. 30, 2026
GBP (£)
Jul. 11, 2023
EUR (€)
Feb. 06, 2023
EUR (€)
Jan. 13, 2022
EUR (€)
Dec. 09, 2021
EUR (€)
May 16, 2021
EUR (€)
Jun. 30, 2026
EUR (€)
Jun. 30, 2026
PLN (zł)
Dec. 31, 1999
shares
Dec. 31, 1994
child
Dec. 31, 2022
EUR (€)
Jun. 30, 2026
GBP (£)
Jun. 30, 2026
PLN (zł)
Mar. 30, 2026
GBP (£)
Dec. 31, 2025
EUR (€)
Dec. 31, 2025
GBP (£)
Dec. 31, 2024
EUR (€)
Dec. 31, 2024
GBP (£)
Nov. 22, 2024
EUR (€)
Jan. 23, 2019
Dec. 31, 2017
EUR (€)
Disclosure of other provisions [line items]                                            
Provisions               € 9,211,000               € 8,355,000            
Banco Popular Espanol S.A.                                            
Disclosure of other provisions [line items]                                            
Estimated cost of compensation to shareholders and bondholders                                           € 680,000
Estimated cost of compensation to shareholders and bondholders applied to the commercial loyalty program                                           € 535,000
Banco Popular’s Compensation Request                                            
Disclosure of other provisions [line items]                                            
Estimated financial effect of contingent liabilities                                       € 2,277,650    
Tax dividend, cum-ex transactions                                            
Disclosure of other provisions [line items]                                            
Provisions               0                            
Individual plaintiff, CEO functions                                            
Disclosure of other provisions [line items]                                            
Provisions               € 35,500                            
Compensation sought in litigation claim             € 112,000         € 61,900                    
Losses on litigation settlements         € 51,400 € 67,800                                
Litigation contingencies, decrease in losses on litigation settlements       € 8,000                                    
Gains on litigation settlements     € 9,600                                      
Individual plaintiff, CEO functions | Share Based Variable Remuneration Award 2018                                            
Disclosure of other provisions [line items]                                            
Variable remuneration, deferred payment, long-term metric achievement, percentage               33.30% 33.30%                          
Individual Plaintiff, CEO Functions, Buy Out Part                                            
Disclosure of other provisions [line items]                                            
Losses on litigation settlements         € 18,600                                  
Spanish Supreme Court, mortgage expenses                                            
Disclosure of other provisions [line items]                                            
Percentage of public notary expenses and agency expenses to be paid                                         50.00%  
Percentage of the registry expenses to be paid                                         100.00%  
Santander Consumer Bank S.A. (Poland)                                            
Disclosure of other provisions [line items]                                            
Mortgage loans denominated in, or indexed to, CHF               € 123,900           zł 523.4                
Santander Consumer Bank S.A. (Poland) | Conversion of active loans from Swiss Francs to PLN Loans                                            
Disclosure of other provisions [line items]                                            
Mortgage loans, provision and adjustment to gross carrying amount               180,400           775.1                
Mortgage loans, adjustment to gross carrying amount               95,400           410.1                
Increase through other costs associated               84,900 zł 365.0                          
Banco Santander Mexico S.A. Institucion De Banca Multiple, Grupo Financiero Santander Mexico | Inheritance trust                                            
Disclosure of other provisions [line items]                                            
Number of sons involved in testamentary trust | child                     4                      
Amount of shares to be transferred by trustee | shares                   36,700,000                        
Provision For Compensation And Associated Cost In Respect Of PPI Policies | Santander Insurance Services UK Limited                                            
Disclosure of other provisions [line items]                                            
Provisions | £                         £ 515.0                  
Provision For Compensation And Associated Cost In Respect Of PPI Policies, Interest | Santander Insurance Services UK Limited                                            
Disclosure of other provisions [line items]                                            
Provisions | £                         162.0                  
Other combined provisions                                            
Disclosure of other provisions [line items]                                            
Provisions               5,795,000               4,993,000            
Other combined provisions | Financial Conduct Authority (FCA) Review of The Vehicle Finance Market | UK                                            
Disclosure of other provisions [line items]                                            
Provisions € 725,000             724,000         £ 623.0   £ 633.0 € 528,100 £ 461.0 € 353,300 £ 293.0      
Increase in existing provisions € 207,000 £ 179.0                                        
Active loans, under IAS 37 | Santander Consumer Bank S.A. (Poland) | Conversion of active loans from Swiss Francs to PLN Loans                                            
Disclosure of other provisions [line items]                                            
Provisions               € 14,700           zł 62.3