| r0.1 | label_boi_a2/To governments | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | boi_SE:x282 | N/A | N/A |
| r0.2 | label_boi_a2/To banks | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | boi_SE:x283 | N/A | N/A |
| r0.3 | label_boi_a2/To others | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | boi_SE:x284 | N/A | N/A |
| r0.4 | label_boi_a2/Balance sheet exposure before deducting local liabilities | boi_met:mi537 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| r0.5 | label_boi_a2/Deduction for local liabilities | boi_met:mi538 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| r0.6 | label_boi_a2/Balance shet exposure after deducting local liabilities | boi_met:mi539 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| r0.7 | label_boi_a2/Total balance sheet exposure Not-detailed | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| r0.8 | label_boi_a2/Total balance sheet exposure | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| r0.9 | label_boi_a2/Probelematic balance credit risk | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| r0.10 | label_boi_a2/Impaired debts | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x3 | N/A |
| r0.11 | label_boi_a2/Total exposure | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x702 | boi_RP:x24 | N/A | N/A | N/A |
| r0.12 | label_boi_a2/Of which: Off balance sheet problematic credit risk | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x702 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| r0.13 | label_boi_a2/Repayment period Up to one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x38 |
| r0.14 | label_boi_a2/Repayment period Over one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | N/A | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x8 |
| 22.1 | Other countries/To governments | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | boi_SE:x282 | N/A | N/A |
| 22.2 | Other countries/To banks | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | boi_SE:x283 | N/A | N/A |
| 22.3 | Other countries/To others | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | boi_SE:x284 | N/A | N/A |
| 22.4 | Other countries/Balance sheet exposure before deducting local liabilities | boi_met:mi537 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 22.5 | Other countries/Deduction for local liabilities | boi_met:mi538 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 22.6 | Other countries/Balance shet exposure after deducting local liabilities | boi_met:mi539 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 22.7 | Other countries/Total balance sheet exposure Not-detailed | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 22.8 | Other countries/Total balance sheet exposure | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 22.9 | Other countries/Probelematic balance credit risk | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| 22.10 | Other countries/Impaired debts | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x3 | N/A |
| 22.11 | Other countries/Total exposure | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x702 | boi_RP:x24 | N/A | N/A | N/A |
| 22.12 | Other countries/Of which: Off balance sheet problematic credit risk | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x702 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| 22.13 | Other countries/Repayment period Up to one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x38 |
| 22.14 | Other countries/Repayment period Over one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x22 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x8 |
| 23.1 | Total exposure to foreign countries/To governments | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | boi_SE:x282 | N/A | N/A |
| 23.2 | Total exposure to foreign countries/To banks | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | boi_SE:x283 | N/A | N/A |
| 23.3 | Total exposure to foreign countries/To others | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | boi_SE:x284 | N/A | N/A |
| 23.4 | Total exposure to foreign countries/Balance sheet exposure before deducting local liabilities | boi_met:mi537 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 23.5 | Total exposure to foreign countries/Deduction for local liabilities | boi_met:mi538 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 23.6 | Total exposure to foreign countries/Balance shet exposure after deducting local liabilities | boi_met:mi539 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 23.7 | Total exposure to foreign countries/Total balance sheet exposure Not-detailed | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 23.8 | Total exposure to foreign countries/Total balance sheet exposure | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 23.9 | Total exposure to foreign countries/Probelematic balance credit risk | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| 23.10 | Total exposure to foreign countries/Impaired debts | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x3 | N/A |
| 23.11 | Total exposure to foreign countries/Total exposure | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x702 | boi_RP:x24 | N/A | N/A | N/A |
| 23.12 | Total exposure to foreign countries/Of which: Off balance sheet problematic credit risk | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x702 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| 23.13 | Total exposure to foreign countries/Repayment period Up to one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x38 |
| 23.14 | Total exposure to foreign countries/Repayment period Over one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x8 |
| 24.1 | Of which: Total exposre to LDC countries/To governments | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | boi_SE:x282 | N/A | N/A |
| 24.2 | Of which: Total exposre to LDC countries/To banks | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | boi_SE:x283 | N/A | N/A |
| 24.3 | Of which: Total exposre to LDC countries/To others | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | boi_SE:x284 | N/A | N/A |
| 24.4 | Of which: Total exposre to LDC countries/Balance sheet exposure before deducting local liabilities | boi_met:mi537 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 24.5 | Of which: Total exposre to LDC countries/Deduction for local liabilities | boi_met:mi538 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 24.6 | Of which: Total exposre to LDC countries/Balance shet exposure after deducting local liabilities | boi_met:mi539 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 24.7 | Of which: Total exposre to LDC countries/Total balance sheet exposure Not-detailed | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 24.8 | Of which: Total exposre to LDC countries/Total balance sheet exposure | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 24.9 | Of which: Total exposre to LDC countries/Probelematic balance credit risk | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| 24.10 | Of which: Total exposre to LDC countries/Impaired debts | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x3 | N/A |
| 24.11 | Of which: Total exposre to LDC countries/Total exposure | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x702 | boi_RP:x24 | N/A | N/A | N/A |
| 24.12 | Of which: Total exposre to LDC countries/Of which: Off balance sheet problematic credit risk | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x702 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| 24.13 | Of which: Total exposre to LDC countries/Repayment period Up to one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x38 |
| 24.14 | Of which: Total exposre to LDC countries/Repayment period Over one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | N/A | boi_GA:x24 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x8 |
| 25.1 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/To governments | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | boi_SE:x282 | N/A | N/A |
| 25.2 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/To banks | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | boi_SE:x283 | N/A | N/A |
| 25.3 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/To others | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | boi_SE:x284 | N/A | N/A |
| 25.4 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Balance sheet exposure before deducting local liabilities | boi_met:mi537 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 25.5 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Deduction for local liabilities | boi_met:mi538 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 25.6 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Balance shet exposure after deducting local liabilities | boi_met:mi539 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 25.7 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Total balance sheet exposure Not-detailed | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 25.8 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Total balance sheet exposure | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | N/A |
| 25.9 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Probelematic balance credit risk | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| 25.10 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Impaired debts | boi_met:mi540 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | boi_ST:x3 | N/A |
| 25.11 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Total exposure | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x702 | boi_RP:x24 | N/A | N/A | N/A |
| 25.12 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Of which: Off balance sheet problematic credit risk | boi_met:mi76 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x702 | boi_RP:x24 | N/A | boi_ST:x2 | N/A |
| 25.13 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Repayment period Up to one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x38 |
| 25.14 | Of which: Total exposre such that each country is exposed in % of total assets or 0.51-2 % of total capital/Repayment period Over one year | boi_met:mi536 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_FN:x1 | boi_GA:x27 | boi_GA:x2 | boi_MC:x1 | boi_RP:x24 | N/A | N/A | boi_TI:x8 |