v3.26.1
Note 21 Customer Deposits (Details) - EUR (€)
€ in Millions
Jun. 30, 2026
Dec. 31, 2025
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost € 532,981 € 502,501
SPAIN    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 239,805 228,672
MEXICO    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 106,230 94,699
TURKEY    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 57,902 52,687
South America [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 63,550 56,478
Europe [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 53,458 55,571
Rest of the world [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 12,036 14,394
Demand deposits at amortized cost [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 370,999 360,682
Demand deposits at amortized cost [Member] | SPAIN    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 196,230 192,222
Demand deposits at amortized cost [Member] | MEXICO    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 82,778 77,167
Demand deposits at amortized cost [Member] | TURKEY    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 26,735 27,443
Demand deposits at amortized cost [Member] | South America [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 37,391 34,150
Demand deposits at amortized cost [Member] | Europe [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 22,863 24,758
Demand deposits at amortized cost [Member] | Rest of the world [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 5,003 4,942
Time deposits and other [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 137,207 127,397
Time deposits and other [Member] | SPAIN    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 27,811 23,664
Time deposits and other [Member] | MEXICO    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 19,596 17,493
Time deposits and other [Member] | TURKEY    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 30,741 24,794
Time deposits and other [Member] | South America [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 26,159 22,328
Time deposits and other [Member] | Europe [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 25,867 29,665
Time deposits and other [Member] | Rest of the world [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 7,033 9,452
Repurchase Agreements [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 24,776 14,422
Repurchase Agreements [Member] | SPAIN    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 15,765 12,786
Repurchase Agreements [Member] | MEXICO    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 3,857 38
Repurchase Agreements [Member] | TURKEY    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 426 450
Repurchase Agreements [Member] | South America [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 0 0
Repurchase Agreements [Member] | Europe [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost 4,729 1,148
Repurchase Agreements [Member] | Rest of the world [Member]    
Deposits From Customers By Geographical Area And Instrument [Line Items]    
Deposits from customers at amortised cost € 0 € 0