| r0.1 | label_boi_a2/Consolidated balance sheet | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r0.2 | label_boi_a2/Bank balance sheet | | | | N/A | N/A | boi_CS:x1 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r1.1 | Assets/Consolidated balance sheet | | | | boi_BC:x1 | N/A | boi_CS:x2 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r1.2 | Assets/Bank balance sheet | | | | boi_BC:x1 | N/A | boi_CS:x1 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 1.1 | Cash and deposits with banks/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x9 | N/A | N/A | boi_RP:x24 | boi_SE:x1 |
| 1.2 | Cash and deposits with banks/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x9 | N/A | N/A | boi_RP:x24 | boi_SE:x1 |
| 2.1 | Securities/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x29 | N/A | N/A | boi_RP:x24 | N/A |
| 2.2 | Securities/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x29 | N/A | N/A | boi_RP:x24 | N/A |
| 3.1 | of which: securities pledged to lenders/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x29 | boi_MC:x29 | N/A | boi_RP:x24 | N/A |
| 3.2 | of which: securities pledged to lenders/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x29 | boi_MC:x29 | N/A | boi_RP:x24 | N/A |
| 4.1 | of which: fair value/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x29 | N/A | boi_PL:x37 | boi_RP:x24 | N/A |
| 4.2 | of which: fair value/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x29 | N/A | boi_PL:x37 | boi_RP:x24 | N/A |
| 5.1 | Securities borrowed or purchased under agreements to resale/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x28 | N/A | N/A | boi_RP:x24 | N/A |
| 5.2 | Securities borrowed or purchased under agreements to resale/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x28 | N/A | N/A | boi_RP:x24 | N/A |
| 6.1 | Credit to the public/Consolidated balance sheet | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 |
| 6.2 | Credit to the public/Bank balance sheet | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 |
| 7.1 | Allowance for loan losses/Consolidated balance sheet | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 |
| 7.2 | Allowance for loan losses/Bank balance sheet | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 |
| 8.1 | Credit to the public, net/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 |
| 8.2 | Credit to the public, net/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 |
| 9.1 | Credit to government/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x11 |
| 9.2 | Credit to government/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x11 |
| 10.1 | Investments in companies included on an equity basis/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x54 | N/A | N/A | boi_RP:x24 | N/A |
| 10.2 | Investments in companies included on an equity basis/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x54 | N/A | N/A | boi_RP:x24 | N/A |
| 11.1 | Buildings and equipment/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x6 | N/A | N/A | boi_RP:x24 | N/A |
| 11.2 | Buildings and equipment/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x6 | N/A | N/A | boi_RP:x24 | N/A |
| 12.1 | Intangible assets and goodwill/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x19 | N/A | N/A | boi_RP:x24 | N/A |
| 12.2 | Intangible assets and goodwill/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x19 | N/A | N/A | boi_RP:x24 | N/A |
| 13.1 | Assets-derivative instruments/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x18 | N/A | N/A | boi_RP:x24 | N/A |
| 13.2 | Assets-derivative instruments/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x18 | N/A | N/A | boi_RP:x24 | N/A |
| 14.1 | Other assets/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x41 | N/A | N/A | boi_RP:x24 | N/A |
| 14.2 | Other assets/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x41 | N/A | N/A | boi_RP:x24 | N/A |
| 15.1 | Total assets/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x1 | N/A | N/A | boi_RP:x24 | N/A |
| 15.2 | Total assets/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x1 | N/A | N/A | boi_RP:x24 | N/A |
| r17.1 | Liabilities and equity capital/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | N/A | N/A | boi_CS:x2 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r17.2 | Liabilities and equity capital/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | N/A | N/A | boi_CS:x1 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 16.1 | Deposits of the public/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x16 |
| 16.2 | Deposits of the public/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x1 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x16 |
| 17.1 | Deposits from banks/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x1 |
| 17.2 | Deposits from banks/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x1 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x1 |
| 18.1 | Deposits from governments/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x11 |
| 18.2 | Deposits from governments/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x1 | boi_MC:x17 | N/A | N/A | boi_RP:x24 | boi_SE:x11 |
| 19.1 | Securities loaned or sold under agreements to repurchase/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | boi_MC:x28 | N/A | N/A | boi_RP:x24 | N/A |
| 19.2 | Securities loaned or sold under agreements to repurchase/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x1 | boi_MC:x28 | N/A | N/A | boi_RP:x24 | N/A |
| 20.1 | Debentures and subordinated notes/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | boi_MC:x15 | N/A | N/A | boi_RP:x24 | N/A |
| 20.2 | Debentures and subordinated notes/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x1 | boi_MC:x15 | N/A | N/A | boi_RP:x24 | N/A |
| 21.1 | Liabilities-derivative instruments/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | boi_MC:x18 | N/A | N/A | boi_RP:x24 | N/A |
| 21.2 | Liabilities-derivative instruments/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x1 | boi_MC:x18 | N/A | N/A | boi_RP:x24 | N/A |
| 22.1 | Other liabilities/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | boi_MC:x20 | N/A | N/A | boi_RP:x24 | N/A |
| 22.2 | Other liabilities/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x1 | boi_MC:x20 | N/A | N/A | boi_RP:x24 | N/A |
| 23.1 | of which: Provision for off balance sheet credit loss allowance and off balance sheet credit instruments/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | boi_MC:x26 | N/A | N/A | boi_RP:x24 | N/A |
| 23.2 | of which: Provision for off balance sheet credit loss allowance and off balance sheet credit instruments/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x1 | boi_MC:x26 | N/A | N/A | boi_RP:x24 | N/A |
| 24.1 | Total liabilities/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | boi_MC:x3 | N/A | N/A | boi_RP:x24 | N/A |
| 24.2 | Total liabilities/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x1 | boi_MC:x3 | N/A | N/A | boi_RP:x24 | N/A |
| 25.1 | Noncontrolling intrests/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CN:x2 | boi_CS:x2 | boi_MC:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 25.2 | Noncontrolling intrests/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CN:x2 | boi_CS:x1 | boi_MC:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 26.1 | Equity capital attributed to shareholders of the banking corporation/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CN:x1 | boi_CS:x2 | boi_MC:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 26.2 | Equity capital attributed to shareholders of the banking corporation/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CN:x1 | boi_CS:x1 | boi_MC:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 27.1 | Total equity/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | N/A | boi_CS:x2 | boi_MC:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 27.2 | Total equity/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | N/A | boi_CS:x1 | boi_MC:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 28.1 | Total liabilities and capital/Consolidated balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x4 | N/A | boi_CS:x2 | boi_MC:x4 | N/A | N/A | boi_RP:x24 | N/A |
| 28.2 | Total liabilities and capital/Bank balance sheet | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x4 | N/A | boi_CS:x1 | boi_MC:x4 | N/A | N/A | boi_RP:x24 | N/A |