| r0.1 | label_boi_a2/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | N/A | boi_MU:x1 | boi_RP:x25 |
| r0.2 | label_boi_a2/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | N/A | N/A | boi_MU:x1 | boi_RP:x25 |
| 1.1 | Profit from the realization of assets received for settlement of loans/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_MC:x155 | N/A | boi_MU:x1 | boi_RP:x25 |
| 1.2 | Profit from the realization of assets received for settlement of loans/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_MC:x155 | N/A | boi_MU:x1 | boi_RP:x25 |
| 2.1 | Capital gain from sale of buildings and equipment/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_MC:x156 | N/A | boi_MU:x1 | boi_RP:x25 |
| 2.2 | Capital gain from sale of buildings and equipment/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_MC:x156 | N/A | boi_MU:x1 | boi_RP:x25 |
| 3.1 | Capital loss from sale of buildings and equipment/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_MC:x157 | N/A | boi_MU:x1 | boi_RP:x25 |
| 3.2 | Capital loss from sale of buildings and equipment/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_MC:x157 | N/A | boi_MU:x1 | boi_RP:x25 |
| 4.1 | Management fee from related companies/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_MC:x158 | N/A | boi_MU:x1 | boi_RP:x25 |
| 4.2 | Management fee from related companies/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_MC:x158 | N/A | boi_MU:x1 | boi_RP:x25 |
| 5.1 | Other/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_MC:x159 | N/A | boi_MU:x1 | boi_RP:x25 |
| 5.2 | Other/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_MC:x159 | N/A | boi_MU:x1 | boi_RP:x25 |
| 6.1 | Total other income/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_MC:x153 | N/A | boi_MU:x1 | boi_RP:x25 |
| 6.2 | Total other income/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_MC:x153 | N/A | boi_MU:x1 | boi_RP:x25 |
| 7.1 | Of which: In respect of sale and leaseback transactions of buildings and equipment/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_MC:x1153 | boi_MC:x929 | boi_MU:x1 | boi_RP:x25 |
| 7.2 | Of which: In respect of sale and leaseback transactions of buildings and equipment/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_MC:x1153 | boi_MC:x929 | boi_MU:x1 | boi_RP:x25 |