| r0.1 | label_boi_a2/Basel III | | | | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| r1.1 | Capital for calculation of capital ratio/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 1.1 | Tier 1 equity capital, after supervisory reconciliations and deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x193 | boi_RP:x24 | N/A |
| 2.1 | Tier 1 additional Tier 1 capital, after deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x219 | boi_RP:x24 | N/A |
| 3.1 | Tier 2 capital, after deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x229 | boi_RP:x24 | N/A |
| 4.1 | Total overall capital/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x192 | boi_RP:x24 | N/A |
| r6.1 | Weighted balances of risk assets/Basel III | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 5.1 | Credit risk/Basel III | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_RT:x21 |
| 6.1 | Market risk/Basel III | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_MC:x57 | N/A | boi_RP:x24 | boi_RT:x3 |
| 7.1 | Operational risk/Basel III | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_RT:x5 |
| 8.1 | Total weighted balances of risk assets/Basel III | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| r11.1 | Ratio of capital to risk assets/Basel III | | | | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 9.1 | Ratio of Tier 1 equity capital to risk assets/Basel III | boi_met:pi37 | num:percentItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 10.1 | Ratio of overall capital to risk assets/Basel III | boi_met:pi38 | num:percentItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 11.1 | Minimum Tier 1 equity capital ratio required by Supervisor of Banks/Basel III | boi_met:pi39 | num:percentItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 12.1 | Minimum overall capital ratio required by Supervisor of Banks/Basel III | boi_met:pi40 | num:percentItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| r16.1 | Capital components for purpose of calculating capital ratio/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| r17.1 | Tier 1 equity capital/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 13.1 | Equity/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x578 | boi_RP:x24 | N/A |
| 14.1 | Differences between equity capital and Tier 1 equity capital/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x204 | boi_RP:x24 | N/A |
| 15.1 | Total tier 1 equity capital before supervisory reconciliations and subtractions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x194 | boi_RP:x24 | N/A |
| r21.1 | Supervisory reconciliations and deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 16.1 | Goodwill and intangible assets/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x206 | boi_RP:x24 | N/A |
| 17.1 | Deferred taxes receivable/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x579 | boi_RP:x24 | N/A |
| 18.1 | Investments in capital of unconsolidated financial corporations/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x580 | boi_RP:x24 | N/A |
| 19.1 | Other supervisory reconciliations and deductions - Tier 1 equity capital/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x1083 | boi_RP:x24 | N/A |
| 20.1 | Total regulatory adjustments and deductions, before adjustments for streamlining program reconciliations/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x1084 | boi_RP:x24 | N/A |
| 21.1 | Total streamlining program reconciliations/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x1082 | boi_RP:x24 | N/A |
| 22.1 | Total supervisory reconciliations and deductions - Tier 1 equity capital/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x205 | boi_RP:x24 | N/A |
| 23.1 | Total Tier 1 equity capital, after supervisory reconciliations and deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x193 | boi_RP:x24 | N/A |
| r30.1 | Tier 1 additional capital/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 24.1 | Instruments and surpluses before deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x220 | boi_RP:x24 | N/A |
| 25.1 | Total deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x225 | boi_RP:x24 | N/A |
| 26.1 | Total tier 1 additional capital after deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x219 | boi_RP:x24 | N/A |
| r34.1 | Tier 2 capital/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 27.1 | Tier 2 capital: instruments, before deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x582 | boi_RP:x24 | N/A |
| 28.1 | Tier 2 capital: allowances, before deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x235 | boi_RP:x24 | N/A |
| 29.1 | Total Tier 2 capital, before deductions/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x230 | boi_RP:x24 | N/A |
| 30.1 | Total deductions: Tier 2 capital/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x236 | boi_RP:x24 | N/A |
| 31.1 | Total Tier 2 capital/Basel III | boi_met:mi15 | xbrli:monetaryItemType | instant | boi_BC:x15 | boi_CS:x2 | N/A | boi_MC:x229 | boi_RP:x24 | N/A |
| r40.1 | Tier 1 equity capital to risk components ratio - details/Basel III | | | | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 32.1 | Tier 1 equity capital to risk components ratio before application of the effect of transitional directives and streamlining program reconciliations/Basel III | boi_met:pi1193 | num:percentItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 33.1 | Effect of the transitional directives/Basel III | boi_met:pi1194 | num:percentItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 34.1 | Tier 1 equity capital to risk components ratio before streamlining program reconciliations/Basel III | boi_met:pi1195 | num:percentItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 35.1 | Streamlining program reconciliations/Basel III | boi_met:pi1196 | num:percentItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 36.1 | Tier 1 equity capital to risk components ratio/Basel III | boi_met:pi37 | num:percentItemType | instant | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A |