Related party transactions (Details 1) - shares
shares in Thousands |
12 Months Ended |
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
| Stockholders Sterrebeeck B V [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
1,809,583
|
1,809,583
|
1,809,583
|
| Ownership interest common shares, percentage |
47.40%
|
47.40%
|
47.40%
|
| Ownership interest, preferred shares |
1,733,644
|
1,733,644
|
1,733,644
|
| Ownership interest preferred shares, percentage |
47.10%
|
47.10%
|
47.10%
|
| Ownership interest, total shares |
3,543,227
|
3,543,227
|
3,543,227
|
| Ownership interest total shares, total |
47.30%
|
47.30%
|
47.30%
|
| Stockholders Grupo Empresarial Santander S L [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
1,627,891
|
1,627,891
|
1,627,891
|
| Ownership interest common shares, percentage |
42.60%
|
42.60%
|
42.60%
|
| Ownership interest, preferred shares |
1,539,863
|
1,539,863
|
1,539,863
|
| Ownership interest preferred shares, percentage |
41.90%
|
41.90%
|
41.90%
|
| Ownership interest, total shares |
3,167,755
|
3,167,754
|
3,167,754
|
| Ownership interest total shares, total |
42.20%
|
42.20%
|
42.20%
|
| Stockholders Banco Santander S A [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
2,696
|
2,696
|
2,696
|
| Ownership interest common shares, percentage |
0.10%
|
0.10%
|
0.10%
|
| Ownership interest, preferred shares |
|
|
|
| Ownership interest preferred shares, percentage |
|
|
|
| Ownership interest, total shares |
2,696
|
2,696
|
2,696
|
| Ownership interest total shares, total |
|
|
|
| Stockholders Directors [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
3,083
|
2,828
|
|
| Ownership interest common shares, percentage |
0.10%
|
0.10%
|
|
| Ownership interest, preferred shares |
3,083
|
2,828
|
|
| Ownership interest preferred shares, percentage |
0.10%
|
0.10%
|
|
| Ownership interest, total shares |
6,167
|
5,656
|
|
| Ownership interest total shares, total |
0.10%
|
0.10%
|
|
| Stockholders Other [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
361,775
|
356,245
|
348,148
|
| Ownership interest common shares, percentage |
9.50%
|
9.30%
|
9.10%
|
| Ownership interest, preferred shares |
389,579
|
384,050
|
375,952
|
| Ownership interest preferred shares, percentage |
10.60%
|
10.40%
|
10.20%
|
| Ownership interest, total shares |
751,354
|
740,295
|
724,100
|
| Ownership interest total shares, total |
10.00%
|
9.90%
|
9.80%
|
| Stockholders Total [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
3,805,028
|
3,799,243
|
3,791,502
|
| Ownership interest common shares, percentage |
99.60%
|
99.50%
|
99.30%
|
| Ownership interest, preferred shares |
3,666,169
|
3,660,385
|
3,652,643
|
| Ownership interest preferred shares, percentage |
99.60%
|
99.50%
|
99.30%
|
| Ownership interest, total shares |
7,471,199
|
7,459,628
|
7,444,145
|
| Ownership interest total shares, total |
99.60%
|
99.50%
|
99.30%
|
| Treasury Share [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
13,666
|
19,452
|
27,193
|
| Ownership interest common shares, percentage |
0.40%
|
0.50%
|
0.70%
|
| Ownership interest, preferred shares |
13,666
|
19,452
|
27,193
|
| Ownership interest preferred shares, percentage |
0.40%
|
0.50%
|
0.70%
|
| Ownership interest, total shares |
27,332
|
38,904
|
54,386
|
| Ownership interest total shares, total |
0.40%
|
0.50%
|
0.70%
|
| Stockholders And Treasury Shares Total [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
3,818,694
|
3,818,695
|
3,818,695
|
| Ownership interest common shares, percentage |
100.00%
|
100.00%
|
100.00%
|
| Ownership interest, preferred shares |
3,679,835
|
3,679,837
|
3,679,836
|
| Ownership interest preferred shares, percentage |
100.00%
|
100.00%
|
100.00%
|
| Ownership interest, total shares |
7,498,531
|
7,498,532
|
7,498,531
|
| Ownership interest total shares, total |
100.00%
|
100.00%
|
100.00%
|
| Stockholders Free Float [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
361,775
|
356,245
|
348,148
|
| Ownership interest common shares, percentage |
9.50%
|
9.30%
|
10.10%
|
| Ownership interest, preferred shares |
389,579
|
384,050
|
375,952
|
| Ownership interest preferred shares, percentage |
10.60%
|
10.40%
|
10.20%
|
| Ownership interest, total shares |
751,354
|
740,295
|
724,100
|
| Ownership interest total shares, total |
10.00%
|
9.90%
|
9.70%
|
| Administrators [Member] |
|
|
|
| IfrsStatementLineItems [Line Items] |
|
|
|
| Ownership interest, common shares |
|
|
3,184
|
| Ownership interest common shares, percentage |
|
|
0.10%
|
| Ownership interest, preferred shares |
|
|
3,184
|
| Ownership interest preferred shares, percentage |
|
|
0.10%
|
| Ownership interest, total shares |
|
|
6,368
|
| Ownership interest total shares, total |
|
|
0.10%
|