| r0.1 | label_boi_a2/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | N/A | N/A | N/A | boi_MU:x1 | N/A | N/A | boi_RP:x25 |
| r0.2 | label_boi_a2/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x1 | N/A | N/A | N/A | boi_MU:x1 | N/A | N/A | boi_RP:x25 |
| 1.1 | Total from activites in derivatie instruments/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x127 | boi_MC:x18 | boi_MU:x1 | boi_PL:x16 | N/A | boi_RP:x25 |
| 1.2 | Total from activites in derivatie instruments/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | N/A | boi_MC:x127 | boi_MC:x18 | boi_MU:x1 | boi_PL:x16 | N/A | boi_RP:x25 |
| r2.1 | A. 2 From investment in bonds/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_MC:x15 | boi_MU:x1 | N/A | N/A | boi_RP:x25 |
| r2.2 | A. 2 From investment in bonds/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x1 | N/A | N/A | boi_MC:x15 | boi_MU:x1 | N/A | N/A | boi_RP:x25 |
| 2.1 | Gains on sale of debentures held to maturity/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x132 | boi_MC:x15 | boi_MU:x1 | boi_PL:x5 | N/A | boi_RP:x25 |
| 2.2 | Gains on sale of debentures held to maturity/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x1 | N/A | boi_MC:x132 | boi_MC:x15 | boi_MU:x1 | boi_PL:x5 | N/A | boi_RP:x25 |
| 3.1 | Losses on sale of debentures held to maturity/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | N/A | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x5 | N/A | boi_RP:x25 |
| 3.2 | Losses on sale of debentures held to maturity/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | N/A | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x5 | N/A | boi_RP:x25 |
| 4.1 | Of which: Provision for writedown/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x126 | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x5 | N/A | boi_RP:x25 |
| 4.2 | Of which: Provision for writedown/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | boi_MC:x126 | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x5 | N/A | boi_RP:x25 |
| 5.1 | Gains on sale of debentors available fo sale/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x132 | boi_MC:x15 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 5.2 | Gains on sale of debentors available fo sale/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x1 | N/A | boi_MC:x132 | boi_MC:x15 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 6.1 | Provisions for impairment in respect of debentors available fo sale/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x126 | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 6.2 | Provisions for impairment in respect of debentors available fo sale/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | boi_MC:x126 | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 7.1 | Losses on sale of debentures available for sale/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x923 | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 7.2 | Losses on sale of debentures available for sale/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | boi_MC:x923 | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 8.1 | Of which: In respect of transfer of bonds/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x923 | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x1 | boi_PL:x2 | boi_RP:x25 |
| 8.2 | Of which: In respect of transfer of bonds/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | boi_MC:x923 | boi_MC:x133 | boi_MC:x15 | boi_MU:x1 | boi_PL:x1 | boi_PL:x2 | boi_RP:x25 |
| 9.1 | Total from investment in debentors/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x131 | boi_MC:x15 | boi_MU:x1 | boi_PL:x14 | N/A | boi_RP:x25 |
| 9.2 | Total from investment in debentors/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | N/A | boi_MC:x131 | boi_MC:x15 | boi_MU:x1 | boi_PL:x14 | N/A | boi_RP:x25 |
| 10.1 | A. 3 Exchange rate differentials/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x139 | N/A | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 10.2 | A. 3 Exchange rate differentials/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | N/A | boi_MC:x139 | N/A | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| r12.1 | A. 4 Gains (losses) on investment in shares/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | N/A | N/A | N/A | boi_MU:x1 | N/A | N/A | boi_RP:x25 |
| r12.2 | A. 4 Gains (losses) on investment in shares/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x1 | N/A | N/A | N/A | boi_MU:x1 | N/A | N/A | boi_RP:x25 |
| 11.1 | Profits from sale of non trade shares/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x132 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 11.2 | Profits from sale of non trade shares/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x1 | N/A | boi_MC:x132 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 12.1 | Provision for write-down of non trade shares/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x126 | boi_MC:x133 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 12.2 | Provision for write-down of non trade shares/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | boi_MC:x126 | boi_MC:x133 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 13.1 | Losses from sale of non trade shares/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x923 | boi_MC:x133 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 13.2 | Losses from sale of non trade shares/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | boi_MC:x923 | boi_MC:x133 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 14.1 | Dividend from non trade shares/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x137 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 14.2 | Dividend from non trade shares/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x1 | N/A | boi_MC:x137 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 15.1 | Unrealised financial gains/losses/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x134 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 15.2 | Unrealised financial gains/losses/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | N/A | boi_MC:x134 | boi_MC:x30 | boi_MU:x1 | boi_PL:x1 | N/A | boi_RP:x25 |
| 16.1 | Gain on sale of shares of investee companies (consolidated affiliated)/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x132 | boi_MC:x54 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 16.2 | Gain on sale of shares of investee companies (consolidated affiliated)/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x1 | N/A | boi_MC:x132 | boi_MC:x54 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 17.1 | Losses on sale of shares of investee companies (consolidated affiliated)/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | N/A | boi_MC:x133 | boi_MC:x54 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 17.2 | Losses on sale of shares of investee companies (consolidated affiliated)/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | N/A | boi_MC:x133 | boi_MC:x54 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 18.1 | Total from investment in shares/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x129 | boi_MC:x246 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 18.2 | Total from investment in shares/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | N/A | boi_MC:x129 | boi_MC:x246 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 19.1 | A. 6 Gains (Losses) in respect of securitisation transactions, Net/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x131 | boi_MC:x138 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 19.2 | A. 6 Gains (Losses) in respect of securitisation transactions, Net/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | N/A | boi_MC:x131 | boi_MC:x138 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 20.1 | A. 6 Gains (Losses) in respect of sold loans, Net/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x131 | boi_MC:x140 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 20.2 | A. 6 Gains (Losses) in respect of sold loans, Net/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | N/A | boi_MC:x131 | boi_MC:x140 | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 21.1 | Total non-interest financing income in respect of activities not for trading purposes/Consolidated | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x128 | N/A | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |
| 21.2 | Total non-interest financing income in respect of activities not for trading purposes/Bank Corporation | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | N/A | boi_MC:x128 | N/A | boi_MU:x1 | boi_PL:x15 | N/A | boi_RP:x25 |