v3.26.1
Shareholder remuneration system and earnings per share - Narrative (Details) - EUR (€)
€ / shares in Units, € in Millions
5 Months Ended 11 Months Ended
May 05, 2026
Jan. 09, 2026
Apr. 04, 2025
Jun. 27, 2025
Dec. 31, 2026
Earnings per share [line items]          
Share buyback program, percentage of underlying profit         25.00%
Share buyback program, percentage of capital released of sale of Poland         50.00%
Agreement for the sale of Santander Bank Polska S.A. | Santander Bank Polska SA          
Earnings per share [line items]          
Sale of proportion of ownership interest in subsidiary   49.00%      
2025 Program, Second          
Earnings per share [line items]          
Share buyback program, amount         € 5,030
2025 Program, Second, Group Underlying Profit          
Earnings per share [line items]          
Share buyback program, amount         1,830
2025 Program, Second, Capital Released Of Poland Sale          
Earnings per share [line items]          
Share buyback program, amount         € 3,200
2024 Program, Second          
Earnings per share [line items]          
Share buyback program, amount       € 1,587  
Complementary Dividend          
Earnings per share [line items]          
Dividends recognised as distributions to owners per share (in euro per share) € 0.125   € 0.11