| r0.1 | label_boi_a2/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | boi_FN:x1 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r0.2 | label_boi_a2/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| r0.3 | label_boi_a2/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| r0.4 | label_boi_a2/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| r0.5 | label_boi_a2/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | N/A | boi_CS:x2 | boi_FN:x1 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r1.1 | Assets/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r1.2 | Assets/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| r1.3 | Assets/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| r1.4 | Assets/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| r1.5 | Assets/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 1.1 | Cash and deposits at banks/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x9 | N/A | N/A | boi_RP:x24 | boi_SE:x1 |
| 1.2 | Cash and deposits at banks/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x9 | N/A | boi_PL:x38 | boi_RP:x24 | boi_SE:x1 |
| 1.3 | Cash and deposits at banks/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x9 | N/A | boi_PL:x39 | boi_RP:x24 | boi_SE:x1 |
| 1.4 | Cash and deposits at banks/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x9 | N/A | boi_PL:x40 | boi_RP:x24 | boi_SE:x1 |
| 1.5 | Cash and deposits at banks/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x9 | N/A | N/A | boi_RP:x24 | boi_SE:x1 |
| 2.1 | Receivables in respect of account of credit card activity, net/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x89 |
| 2.2 | Receivables in respect of account of credit card activity, net/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x8 | N/A | boi_PL:x38 | boi_RP:x24 | boi_SE:x89 |
| 2.3 | Receivables in respect of account of credit card activity, net/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x8 | N/A | boi_PL:x39 | boi_RP:x24 | boi_SE:x89 |
| 2.4 | Receivables in respect of account of credit card activity, net/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x8 | N/A | boi_PL:x40 | boi_RP:x24 | boi_SE:x89 |
| 2.5 | Receivables in respect of account of credit card activity, net/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x89 |
| 3.1 | Securities/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x29 | N/A | N/A | boi_RP:x24 | N/A |
| 3.2 | Securities/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x29 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 3.3 | Securities/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x29 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 3.4 | Securities/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x29 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 3.5 | Securities/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x29 | N/A | N/A | boi_RP:x24 | N/A |
| 4.1 | Securities borrowed or purchased under resale agreements/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | N/A | boi_RP:x24 | N/A |
| 4.2 | Securities borrowed or purchased under resale agreements/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 4.3 | Securities borrowed or purchased under resale agreements/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 4.4 | Securities borrowed or purchased under resale agreements/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 4.5 | Securities borrowed or purchased under resale agreements/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | N/A | boi_RP:x24 | N/A |
| 5.1 | Other financial assets/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x443 | N/A | N/A | boi_RP:x24 | N/A |
| 5.2 | Other financial assets/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x443 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 5.3 | Other financial assets/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x443 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 5.4 | Other financial assets/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x443 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 5.5 | Other financial assets/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x443 | N/A | N/A | boi_RP:x24 | N/A |
| 6.1 | Total financial assets/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | N/A | N/A | boi_RP:x24 | N/A |
| 6.2 | Total financial assets/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 6.3 | Total financial assets/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 6.4 | Total financial assets/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 6.5 | Total financial assets/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | N/A | N/A | boi_RP:x24 | N/A |
| 7.1 | Of which: Assets whose balance-sheet balance is equal to the fair value/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | boi_PL:x37 | N/A | boi_RP:x24 | N/A |
| 7.2 | Of which: Assets whose balance-sheet balance is equal to the fair value/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | boi_PL:x37 | boi_PL:x38 | boi_RP:x24 | N/A |
| 7.3 | Of which: Assets whose balance-sheet balance is equal to the fair value/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | boi_PL:x37 | boi_PL:x39 | boi_RP:x24 | N/A |
| 7.4 | Of which: Assets whose balance-sheet balance is equal to the fair value/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | boi_PL:x37 | boi_PL:x40 | boi_RP:x24 | N/A |
| 7.5 | Of which: Assets whose balance-sheet balance is equal to the fair value/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_MC:x1 | boi_PL:x37 | N/A | boi_RP:x24 | N/A |
| r9.1 | Liabilities/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r9.2 | Liabilities/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| r9.3 | Liabilities/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| r9.4 | Liabilities/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| r9.5 | Liabilities/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 8.1 | Credit from banking corporations/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x1 |
| 8.2 | Credit from banking corporations/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | boi_PL:x38 | boi_RP:x24 | boi_SE:x1 |
| 8.3 | Credit from banking corporations/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | boi_PL:x39 | boi_RP:x24 | boi_SE:x1 |
| 8.4 | Credit from banking corporations/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | boi_PL:x40 | boi_RP:x24 | boi_SE:x1 |
| 8.5 | Credit from banking corporations/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x1 |
| 9.1 | Payables in respect of credit card activity, net/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x89 |
| 9.2 | Payables in respect of credit card activity, net/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | boi_PL:x38 | boi_RP:x24 | boi_SE:x89 |
| 9.3 | Payables in respect of credit card activity, net/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | boi_PL:x39 | boi_RP:x24 | boi_SE:x89 |
| 9.4 | Payables in respect of credit card activity, net/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | boi_PL:x40 | boi_RP:x24 | boi_SE:x89 |
| 9.5 | Payables in respect of credit card activity, net/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x89 |
| 10.1 | Deposits of the government/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x592 | N/A | N/A | boi_RP:x24 | N/A |
| 10.2 | Deposits of the government/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x592 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 10.3 | Deposits of the government/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x592 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 10.4 | Deposits of the government/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x592 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 10.5 | Deposits of the government/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x592 | N/A | N/A | boi_RP:x24 | N/A |
| 11.1 | Securities borrowed or sold under repo agreements/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | N/A | boi_RP:x24 | N/A |
| 11.2 | Securities borrowed or sold under repo agreements/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 11.3 | Securities borrowed or sold under repo agreements/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 11.4 | Securities borrowed or sold under repo agreements/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 11.5 | Securities borrowed or sold under repo agreements/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x28 | N/A | N/A | boi_RP:x24 | N/A |
| 12.1 | Bonds and subordinated notes/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x15 | N/A | N/A | boi_RP:x24 | N/A |
| 12.2 | Bonds and subordinated notes/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x15 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 12.3 | Bonds and subordinated notes/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x15 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 12.4 | Bonds and subordinated notes/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x15 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 12.5 | Bonds and subordinated notes/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x15 | N/A | N/A | boi_RP:x24 | N/A |
| 13.1 | Other financial liabilities/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x593 | N/A | N/A | boi_RP:x24 | N/A |
| 13.2 | Other financial liabilities/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x593 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 13.3 | Other financial liabilities/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x593 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 13.4 | Other financial liabilities/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x593 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 13.5 | Other financial liabilities/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x593 | N/A | N/A | boi_RP:x24 | N/A |
| 14.1 | Total financial liabilities/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | N/A | N/A | boi_RP:x24 | N/A |
| 14.2 | Total financial liabilities/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 14.3 | Total financial liabilities/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 14.4 | Total financial liabilities/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 14.5 | Total financial liabilities/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | N/A | N/A | boi_RP:x24 | N/A |
| 15.1 | Of which: Assets whose balance-sheet balance is equal to the fair value/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | boi_PL:x37 | N/A | boi_RP:x24 | N/A |
| 15.2 | Of which: Assets whose balance-sheet balance is equal to the fair value/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | boi_PL:x37 | boi_PL:x38 | boi_RP:x24 | N/A |
| 15.3 | Of which: Assets whose balance-sheet balance is equal to the fair value/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | boi_PL:x37 | boi_PL:x39 | boi_RP:x24 | N/A |
| 15.4 | Of which: Assets whose balance-sheet balance is equal to the fair value/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | boi_PL:x37 | boi_PL:x40 | boi_RP:x24 | N/A |
| 15.5 | Of which: Assets whose balance-sheet balance is equal to the fair value/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_FN:x1 | boi_MC:x3 | boi_PL:x37 | N/A | boi_RP:x24 | N/A |
| 16.1 | Off-balance-sheet financial instruments: Transactions in which the balance represents credit risk/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x589 | N/A | N/A | boi_RP:x24 | N/A |
| 16.2 | Off-balance-sheet financial instruments: Transactions in which the balance represents credit risk/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x589 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 16.3 | Off-balance-sheet financial instruments: Transactions in which the balance represents credit risk/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x589 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 16.4 | Off-balance-sheet financial instruments: Transactions in which the balance represents credit risk/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x589 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 16.5 | Off-balance-sheet financial instruments: Transactions in which the balance represents credit risk/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x589 | N/A | N/A | boi_RP:x24 | N/A |
| 17.1 | Contingent liabilities and other special commitments/Balance-sheet balance | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x590 | N/A | N/A | boi_RP:x24 | N/A |
| 17.2 | Contingent liabilities and other special commitments/Level 1 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x590 | N/A | boi_PL:x38 | boi_RP:x24 | N/A |
| 17.3 | Contingent liabilities and other special commitments/Level 2 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x590 | N/A | boi_PL:x39 | boi_RP:x24 | N/A |
| 17.4 | Contingent liabilities and other special commitments/Level 3 | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x590 | N/A | boi_PL:x40 | boi_RP:x24 | N/A |
| 17.5 | Contingent liabilities and other special commitments/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_MC:x590 | N/A | N/A | boi_RP:x24 | N/A |