| r0.1 | label_boi_a2/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A | N/A | boi_RP:x19 |
| r0.2 | label_boi_a2/Accumulated from the beginning of year (-1) | 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:x19 |
| r1.1 | A.From activity in derivative instruments/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A | N/A | boi_RP:x19 |
| r1.2 | A.From activity in derivative instruments/Accumulated from the beginning of year (-1) | 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:x19 |
| 1.1 | Total from activity in derivative instruments/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x127 | boi_MC:x18 | N/A | boi_PL:x16 | N/A | boi_RP:x19 |
| 1.2 | Total from activity in derivative instruments/Accumulated from the beginning of year (-1) | 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:x19 |
| r3.1 | A.2 From investment in bonds/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_MC:x15 | N/A | N/A | N/A | boi_RP:x19 |
| r3.2 | A.2 From investment in bonds/Accumulated from the beginning of year (-1) | 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:x19 |
| 2.1 | Gain from sale of bonds held to maturity/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x132 | boi_MC:x15 | N/A | boi_PL:x5 | N/A | boi_RP:x19 |
| 2.2 | Gain from sale of bonds held to maturity/Accumulated from the beginning of year (-1) | 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:x19 |
| 3.1 | Losses from sale of bonds held to maturity/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | N/A | boi_MC:x133 | boi_MC:x15 | N/A | boi_PL:x5 | N/A | boi_RP:x19 |
| 3.2 | Losses from sale of bonds held to maturity/Accumulated from the beginning of year (-1) | 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:x19 |
| 4.1 | Of which: Provision for writedown/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x126 | boi_MC:x133 | boi_MC:x15 | N/A | boi_PL:x5 | N/A | boi_RP:x19 |
| 4.2 | Of which: Provision for writedown/Accumulated from the beginning of year (-1) | 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:x19 |
| 5.1 | Gains from sale of bonds available for sale/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x132 | boi_MC:x15 | N/A | boi_PL:x1 | N/A | boi_RP:x19 |
| 5.2 | Gains from sale of bonds available for sale/Accumulated from the beginning of year (-1) | 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:x19 |
| 6.1 | Provision for write-down of bonds available for sale/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x126 | boi_MC:x133 | boi_MC:x15 | N/A | boi_PL:x1 | N/A | boi_RP:x19 |
| 6.2 | Provision for write-down of bonds available for sale/Accumulated from the beginning of year (-1) | 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:x19 |
| 7.1 | Losses from sale of bonds available for sale/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x923 | boi_MC:x133 | boi_MC:x15 | N/A | boi_PL:x1 | N/A | boi_RP:x19 |
| 7.2 | Losses from sale of bonds available for sale/Accumulated from the beginning of year (-1) | 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:x19 |
| 8.1 | Of which: In respect of transfer of bonds to trading portfolio/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x923 | boi_MC:x133 | boi_MC:x15 | N/A | boi_PL:x1 | boi_PL:x2 | boi_RP:x19 |
| 8.2 | Of which: In respect of transfer of bonds to trading portfolio/Accumulated from the beginning of year (-1) | 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:x19 |
| 9.1 | Total from investment in bonds/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x131 | boi_MC:x15 | N/A | boi_PL:x14 | N/A | boi_RP:x19 |
| 9.2 | Total from investment in bonds/Accumulated from the beginning of year (-1) | 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:x19 |
| 10.1 | A.3 Net exchange rate differentials, net/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x139 | N/A | N/A | boi_PL:x15 | N/A | boi_RP:x19 |
| 10.2 | A.3 Net exchange rate differentials, net/Accumulated from the beginning of year (-1) | 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:x19 |
| r13.1 | A.4 Profits (Losses) from investments in shares/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A | N/A | boi_RP:x19 |
| r13.2 | A.4 Profits (Losses) from investments in shares/Accumulated from the beginning of year (-1) | 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:x19 |
| 11.1 | Profits from sale of non trade shares/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x132 | boi_MC:x30 | N/A | boi_PL:x1 | N/A | boi_RP:x19 |
| 11.2 | Profits from sale of non trade shares/Accumulated from the beginning of year (-1) | 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:x19 |
| 12.1 | Provision for write-down of non trade shares/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x126 | boi_MC:x133 | boi_MC:x30 | N/A | boi_PL:x1 | N/A | boi_RP:x19 |
| 12.2 | Provision for write-down of non trade shares/Accumulated from the beginning of year (-1) | 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:x19 |
| 13.1 | Losses from sale of non trade shares/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_MC:x923 | boi_MC:x133 | boi_MC:x30 | N/A | boi_PL:x1 | N/A | boi_RP:x19 |
| 13.2 | Losses from sale of non trade shares/Accumulated from the beginning of year (-1) | 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:x19 |
| 14.1 | Dividend from non trade shares/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x137 | boi_MC:x30 | N/A | boi_PL:x1 | N/A | boi_RP:x19 |
| 14.2 | Dividend from non trade shares/Accumulated from the beginning of year (-1) | 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:x19 |
| 15.1 | Unrealised financial gains/losses/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x134 | boi_MC:x30 | N/A | boi_PL:x1 | N/A | boi_RP:x19 |
| 15.2 | Unrealised financial gains/losses/Accumulated from the beginning of year (-1) | 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:x19 |
| 16.1 | Profit from sale of shares of equity-basis investees/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | N/A | boi_MC:x132 | boi_MC:x54 | N/A | boi_PL:x15 | N/A | boi_RP:x19 |
| 16.2 | Profit from sale of shares of equity-basis investees/Accumulated from the beginning of year (-1) | 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:x19 |
| 17.1 | Loss from sale of shares of equity-basis investees/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | N/A | boi_MC:x133 | boi_MC:x54 | N/A | boi_PL:x15 | N/A | boi_RP:x19 |
| 17.2 | Loss from sale of shares of equity-basis investees/Accumulated from the beginning of year (-1) | 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:x19 |
| 18.1 | Total investment in shares/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x129 | boi_MC:x246 | N/A | boi_PL:x15 | N/A | boi_RP:x19 |
| 18.2 | Total investment in shares/Accumulated from the beginning of year (-1) | 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:x19 |
| 19.1 | A.5 Net gain (losses) in respect of securitization transactions/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x131 | boi_MC:x138 | N/A | boi_PL:x15 | N/A | boi_RP:x19 |
| 19.2 | A.5 Net gain (losses) in respect of securitization transactions/Accumulated from the beginning of year (-1) | 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:x19 |
| 20.1 | A.6 Net gains (losses) in respect of loans sold/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x131 | boi_MC:x140 | N/A | boi_PL:x15 | N/A | boi_RP:x19 |
| 20.2 | A.6 Net gains (losses) in respect of loans sold/Accumulated from the beginning of year (-1) | 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:x19 |
| 21.1 | Total non-interest financing income in respect of non-trading activities/Quarter (Year -1) | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | N/A | boi_MC:x128 | N/A | N/A | boi_PL:x15 | N/A | boi_RP:x19 |
| 21.2 | Total non-interest financing income in respect of non-trading activities/Accumulated from the beginning of year (-1) | 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:x19 |