v3.25.2
Additional disclosure requirements - Schedule of preference shares and preferred securities by issuer (Details)
€ in Millions, £ in Millions, $ in Millions
 6 Months Ended
Jun. 30, 2025
EUR (€)
Jun. 30, 2025
GBP (£)
Jun. 30, 2025
USD ($)
Jan. 14, 2020
Santander UK plc, October 1995 | Preference shares        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount | £   £ 80.3    
Interest rate 10.375% 10.375% 10.375%  
Santander UK plc, February 1996 | Preference shares        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount | £   £ 80.3    
Interest rate 10.375% 10.375% 10.375%  
Banco Santander, S.A., January 2020        
Disclosure of detailed information about financial instruments [line items]        
Initial interest rate term 6 years      
Reprice term 5 years      
Subordinated issue, mid-swap rate term 5 years      
Banco Santander, S.A., January 2020 | Preferred securities        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount € 1,498.6      
Interest rate 4.375% 4.375% 4.375% 4.375%
Adjustment to reference rate, after initial interest rate period 4.534% 4.534% 4.534%  
Banco Santander, S.A., May 2021 | US Dollar        
Disclosure of detailed information about financial instruments [line items]        
Initial interest rate term 6 years      
Reprice term 5 years      
Subordinated Issue, UST Rate Term 5 years      
Banco Santander, S.A., May 2021 | Euro        
Disclosure of detailed information about financial instruments [line items]        
Initial interest rate term 7 years      
Reprice term 5 years      
Subordinated issue, mid-swap rate term 5 years      
Banco Santander, S.A., May 2021 | Preferred securities | US Dollar        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount | $     $ 996.5  
Interest rate 4.75% 4.75% 4.75%  
Adjustment to reference rate, after initial interest rate period 3.753% 3.753% 3.753%  
Banco Santander, S.A., May 2021 | Preferred securities | Euro        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount € 750.0      
Interest rate 4.125% 4.125% 4.125%  
Adjustment to reference rate, after initial interest rate period 4.311% 4.311% 4.311%  
Banco Santander, S.A., September 2021 | Preferred securities        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount € 998.0      
Interest rate 3.625% 3.625% 3.625%  
Banco Santander, S.A., September 2021 | Subordinated Liabilities, Preferred Securities        
Disclosure of detailed information about financial instruments [line items]        
Interest rate 3.625% 3.625% 3.625%  
Initial interest rate term 8 years      
Reprice term 5 years      
Subordinated issue, mid-swap rate term 5 years      
Banco Santander, S.A., September 2021 | Mid Swap Rate Five Year Euro | Subordinated Liabilities, Preferred Securities        
Disclosure of detailed information about financial instruments [line items]        
Adjustment to reference rate, after initial interest rate period 3.76% 3.76% 3.76%  
Issuance By Banco Santander S.A. In November 2023, First Series | Subordinated Liabilities, Preferred Securities        
Disclosure of detailed information about financial instruments [line items]        
Interest rate 9.625% 9.625% 9.625%  
Initial interest rate term 5 years 6 months      
Reprice term 5 years      
Subordinated Issue, UST Rate Term 5 years      
Issuance By Banco Santander S.A. In November 2023, First Series | Fixed interest rate [member] | Subordinated Liabilities, Preferred Securities        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount | $     $ 1,147.6  
Interest rate 9.625% 9.625% 9.625%  
Issuance By Banco Santander S.A. In November 2023, First Series | UST Rate Five Year US Dollar | Subordinated Liabilities, Preferred Securities        
Disclosure of detailed information about financial instruments [line items]        
Adjustment to reference rate, after initial interest rate period 5.306% 5.306% 5.306%  
Issuance By Banco Santander S.A. In November 2023, Second Series | Subordinated Liabilities, Preferred Securities        
Disclosure of detailed information about financial instruments [line items]        
Interest rate 9.625% 9.625% 9.625%  
Initial interest rate term 10 years      
Reprice term 5 years      
Subordinated Issue, UST Rate Term 5 years      
Issuance By Banco Santander S.A. In November 2023, Second Series | Fixed interest rate [member] | Subordinated Liabilities, Preferred Securities        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount | $     $ 1,350.0  
Interest rate 9.625% 9.625% 9.625%  
Issuance By Banco Santander S.A. In November 2023, Second Series | UST Rate Five Year US Dollar | Subordinated Liabilities, Preferred Securities        
Disclosure of detailed information about financial instruments [line items]        
Adjustment to reference rate, after initial interest rate period 5.298% 5.298% 5.298%  
Issuance By Banco Santander S.A. In May 2024 | Preferred securities        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount € 1,495.2      
Interest rate 7.00% 7.00% 7.00%  
Initial interest rate term 6 years      
Reprice term 5 years      
Subordinated issue, mid-swap rate term 5 years      
Issuance By Banco Santander S.A. In May 2024 | Mid Swap Rate Five Year Euro | Preferred securities        
Disclosure of detailed information about financial instruments [line items]        
Adjustment to reference rate, after initial interest rate period 4.432% 4.432% 4.432%  
Issuance By Banco Santander S.A. In August 2024 | Preferred securities        
Disclosure of detailed information about financial instruments [line items]        
Interest rate 8.00% 8.00% 8.00%  
Initial interest rate term 10 years      
Reprice term 5 years      
Subordinated issue, mid-swap rate term 5 years      
Issuance By Banco Santander S.A. In August 2024 | Fixed interest rate [member] | Subordinated Liabilities, Preferred Securities        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount | $     $ 1,500.0  
Interest rate 8.00% 8.00% 8.00%  
Issuance By Banco Santander S.A. In August 2024 | Mid Swap Rate Five Year Euro | Preferred securities        
Disclosure of detailed information about financial instruments [line items]        
Adjustment to reference rate, after initial interest rate period 3.911% 3.911% 3.911%  
Santander Finance Preferred, S.A. (Unipersonal), September 2004 | Preferred securities        
Disclosure of detailed information about financial instruments [line items]        
Outstanding issue amount € 143.5      
Santander Finance Preferred, S.A. (Unipersonal), September 2004 | CMS 10 interest rate | Preferred securities        
Disclosure of detailed information about financial instruments [line items]        
Interest rate 8.00% 8.00% 8.00%  
Variable interest rate 0.05% 0.05% 0.05%