v3.26.1
Tax matters - Narrative (Details)
€ in Millions
 12 Months Ended
Dec. 31, 2025
EUR (€)
Dec. 31, 2025
GBP (£)
Dec. 31, 2024
EUR (€)
Dec. 31, 2024
GBP (£)
Dec. 31, 2023
EUR (€)
Dec. 31, 2022
EUR (€)
Disclosure of other provisions [line items]            
Deferred tax assets € 18,944   € 19,170   € 20,767 € 20,787
Deferred tax assets not recognized 11,240          
Tax losses, deferred tax assets not recognized 6,420          
Tax credits, deferred tax assets not recognized 3,430          
Other concepts, deferred tax assets not recognized 1,390          
Taxes other than income tax 543   554   568  
Law 38/2022, Tax Reform            
Disclosure of other provisions [line items]            
Taxes other than income tax     334   224  
Decree-Law 9/2024            
Disclosure of other provisions [line items]            
Payment of tax expense other than income tax expense 392          
Law 7/2024, Tax Reform            
Disclosure of other provisions [line items]            
Taxes other than income tax 353          
Temporary differences            
Disclosure of other provisions [line items]            
Deferred tax assets € 16,590   16,803   18,374 19,009
Deferred tax asset recovery period 15 years 15 years        
Tax losses and tax credits            
Disclosure of other provisions [line items]            
Deferred tax assets € 2,354   2,367   2,393 1,778
Monetizable            
Disclosure of other provisions [line items]            
Deferred tax assets 10,725   10,309   11,099  
Monetizable | Temporary differences            
Disclosure of other provisions [line items]            
Deferred tax assets 10,725   10,309   11,099 € 10,660
Other            
Disclosure of other provisions [line items]            
Deferred tax assets 8,219   8,861   9,668  
Other | Temporary differences            
Disclosure of other provisions [line items]            
Deferred tax assets 5,865   6,494   7,275  
Other | Tax losses and tax credits            
Disclosure of other provisions [line items]            
Deferred tax assets 2,354   € 2,367   € 2,393  
Spain            
Disclosure of other provisions [line items]            
Deferred tax assets 7,183          
Spain | Tax losses and tax credits            
Disclosure of other provisions [line items]            
Deferred tax assets 681          
Spain | Monetizable | Temporary differences            
Disclosure of other provisions [line items]            
Deferred tax assets 5,069          
Spain | Other | Temporary differences            
Disclosure of other provisions [line items]            
Deferred tax assets 1,433          
Brazil            
Disclosure of other provisions [line items]            
Deferred tax assets 7,465          
Brazil | Tax losses and tax credits            
Disclosure of other provisions [line items]            
Deferred tax assets 709          
Brazil | Monetizable | Temporary differences            
Disclosure of other provisions [line items]            
Deferred tax assets 5,606          
Brazil | Other | Temporary differences            
Disclosure of other provisions [line items]            
Deferred tax assets 1,150          
Mexico            
Disclosure of other provisions [line items]            
Deferred tax assets 1,542          
Mexico | Temporary differences            
Disclosure of other provisions [line items]            
Deferred tax assets 1,511          
Mexico | Tax losses and tax credits            
Disclosure of other provisions [line items]            
Deferred tax assets 31          
US            
Disclosure of other provisions [line items]            
Deferred tax assets 1,026          
US | Temporary differences            
Disclosure of other provisions [line items]            
Deferred tax assets 253          
US | Tax losses and tax credits            
Disclosure of other provisions [line items]            
Deferred tax assets € 773          
United Kingdom            
Disclosure of other provisions [line items]            
Dividend exemption, generating potential tax credit | £   £ 500   £ 500    
Actuarial assumption of growth | Spain            
Disclosure of other provisions [line items]            
Percentage used to adjust sensitivity analysis 0.50% 0.50%        
Inflation rate assumption | Spain            
Disclosure of other provisions [line items]            
Percentage used to adjust sensitivity analysis 0.50% 0.50%