Basis of preparation and material accounting policies - Estimated economic useful lives for premises and equipment except for land (Details) |
12 Months Ended |
|---|---|
Dec. 31, 2025 | |
| Buildings used for business purpose | |
| Disclosure of property plant and equipment [Line Items] | |
| Useful life for property plant and equipment | 26 to 57 years |
| Structures in leased office | |
| Disclosure of property plant and equipment [Line Items] | |
| Useful life for property plant and equipment | 4 to 5 years |
| Properties for business purpose | |
| Disclosure of property plant and equipment [Line Items] | |
| Useful life for property plant and equipment | 4 to 7 years |