| r0.1 | label_boi_a2/Commercial | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x4 | N/A | N/A | N/A |
| r0.2 | label_boi_a2/Housing | | | | N/A | boi_CL:x35 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | N/A | N/A | N/A |
| r0.3 | label_boi_a2/Other private | | | | N/A | boi_CL:x38 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | N/A | N/A | N/A |
| r0.4 | label_boi_a2/Total | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | N/A | N/A | N/A |
| r1.1 | Credit risk at credit performance rating/Commercial | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x40 | N/A | N/A |
| r1.2 | Credit risk at credit performance rating/Housing | | | | N/A | boi_CL:x35 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x40 | N/A | N/A |
| r1.3 | Credit risk at credit performance rating/Other private | | | | N/A | boi_CL:x38 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x40 | N/A | N/A |
| r1.4 | Credit risk at credit performance rating/Total | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x40 | N/A | N/A |
| 1.1 | Balance sheet credit risk/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x40 | N/A | N/A |
| 1.2 | Balance sheet credit risk/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x40 | N/A | N/A |
| 1.3 | Balance sheet credit risk/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x40 | N/A | N/A |
| 1.4 | Balance sheet credit risk/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x40 | N/A | N/A |
| 2.1 | Off- balance sheet credit risk/Commercial | boi_met:mi186 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x2 | boi_MC:x65 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x40 | N/A | N/A |
| 2.2 | Off- balance sheet credit risk/Housing | boi_met:mi186 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CL:x35 | boi_CS:x2 | boi_MC:x65 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x40 | N/A | N/A |
| 2.3 | Off- balance sheet credit risk/Other private | boi_met:mi186 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CL:x38 | boi_CS:x2 | boi_MC:x65 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x40 | N/A | N/A |
| 2.4 | Off- balance sheet credit risk/Total | boi_met:mi186 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x2 | boi_MC:x65 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x40 | N/A | N/A |
| 3.1 | Total credit risk at credit performance rating/Commercial | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x40 | N/A | N/A |
| 3.2 | Total credit risk at credit performance rating/Housing | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x40 | N/A | N/A |
| 3.3 | Total credit risk at credit performance rating/Other private | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x40 | N/A | N/A |
| 3.4 | Total credit risk at credit performance rating/Total | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x40 | N/A | N/A |
| r5.1 | Credit risk that is not rated as performing credit/Commercial | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | N/A | N/A |
| r5.2 | Credit risk that is not rated as performing credit/Housing | | | | N/A | boi_CL:x35 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | N/A | N/A |
| r5.3 | Credit risk that is not rated as performing credit/Other private | | | | N/A | boi_CL:x38 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | N/A | N/A |
| r5.4 | Credit risk that is not rated as performing credit/Total | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | N/A | N/A |
| 4.1 | Non problematic/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | boi_ST:x1 | N/A |
| 4.2 | Non problematic/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x1 | N/A |
| 4.3 | Non problematic/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x1 | N/A |
| 4.4 | Non problematic/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | boi_ST:x1 | N/A |
| 5.1 | Total problematic/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | boi_ST:x2 | N/A |
| 5.2 | Total problematic/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x2 | N/A |
| 5.3 | Total problematic/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x2 | N/A |
| 5.4 | Total problematic/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | boi_ST:x2 | N/A |
| 6.1 | Credit risk under special supervising/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | boi_ST:x14 | N/A |
| 6.2 | Credit risk under special supervising/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x14 | N/A |
| 6.3 | Credit risk under special supervising/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x14 | N/A |
| 6.4 | Credit risk under special supervising/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | boi_ST:x14 | N/A |
| 7.1 | Substandard credit risk/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | boi_ST:x15 | N/A |
| 7.2 | Substandard credit risk/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x15 | N/A |
| 7.3 | Substandard credit risk/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x15 | N/A |
| 7.4 | Substandard credit risk/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | boi_ST:x15 | N/A |
| 8.1 | Impaired credit risk/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | boi_ST:x3 | N/A |
| 8.2 | Impaired credit risk/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x3 | N/A |
| 8.3 | Impaired credit risk/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x3 | N/A |
| 8.4 | Impaired credit risk/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | boi_ST:x3 | N/A |
| 9.1 | Total balance sheet credit risk/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | N/A | N/A |
| 9.2 | Total balance sheet credit risk/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | N/A | N/A |
| 9.3 | Total balance sheet credit risk/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | N/A | N/A |
| 9.4 | Total balance sheet credit risk/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x917 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | N/A | N/A |
| 10.1 | Off- balance sheet credit risk/Commercial | boi_met:mi186 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x2 | boi_MC:x65 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | N/A | N/A |
| 10.2 | Off- balance sheet credit risk/Housing | boi_met:mi186 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CL:x35 | boi_CS:x2 | boi_MC:x65 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | N/A | N/A |
| 10.3 | Off- balance sheet credit risk/Other private | boi_met:mi186 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CL:x38 | boi_CS:x2 | boi_MC:x65 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | N/A | N/A |
| 10.4 | Off- balance sheet credit risk/Total | boi_met:mi186 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x2 | boi_MC:x65 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | N/A | N/A |
| 11.1 | Total credit risk not at credit performance rating/Commercial | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | N/A | N/A |
| 11.2 | Total credit risk not at credit performance rating/Housing | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | N/A | N/A |
| 11.3 | Total credit risk not at credit performance rating/Other private | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | N/A | N/A |
| 11.4 | Total credit risk not at credit performance rating/Total | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | N/A | N/A |
| 12.1 | Of which:Unimpaired debts in arrears of 90 days or more/Commercial | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x209 | boi_ST:x4 | boi_TI:x2 |
| 12.2 | Of which:Unimpaired debts in arrears of 90 days or more/Housing | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x4 | boi_TI:x2 |
| 12.3 | Of which:Unimpaired debts in arrears of 90 days or more/Other private | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x209 | boi_ST:x4 | boi_TI:x2 |
| 12.4 | Of which:Unimpaired debts in arrears of 90 days or more/Total | boi_met:mi476 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x209 | boi_ST:x4 | boi_TI:x2 |
| 13.1 | Overall credit risk to the public/Commercial | boi_met:mi468 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x4 | N/A | N/A | N/A |
| 13.2 | Overall credit risk to the public/Housing | boi_met:mi468 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x15 | N/A | N/A | N/A |
| 13.3 | Overall credit risk to the public/Other private | boi_met:mi468 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x15 | N/A | N/A | N/A |
| 13.4 | Overall credit risk to the public/Total | boi_met:mi468 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x928 | N/A | boi_RP:x24 | boi_SE:x16 | N/A | N/A | N/A |
| r16.1 | Non performing assets/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | N/A | boi_MC:x914 | boi_RP:x24 | boi_SE:x4 | N/A | N/A | N/A |
| r16.2 | Non performing assets/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | N/A | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | N/A | N/A | N/A |
| r16.3 | Non performing assets/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | N/A | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | N/A | N/A | N/A |
| r16.4 | Non performing assets/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | N/A | boi_MC:x914 | boi_RP:x24 | boi_SE:x16 | N/A | N/A | N/A |
| 14.1 | Impaired debts/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x917 | boi_MC:x914 | boi_RP:x24 | boi_SE:x4 | N/A | boi_ST:x3 | N/A |
| 14.2 | Impaired debts/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x917 | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| 14.3 | Impaired debts/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x917 | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| 14.4 | Impaired debts/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x917 | boi_MC:x914 | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x3 | N/A |
| 15.1 | Assets received in respect of credit repaid/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x637 | boi_MC:x914 | boi_RP:x24 | boi_SE:x4 | N/A | N/A | N/A |
| 15.2 | Assets received in respect of credit repaid/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x637 | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | N/A | N/A | N/A |
| 15.3 | Assets received in respect of credit repaid/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x637 | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | N/A | N/A | N/A |
| 15.4 | Assets received in respect of credit repaid/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x637 | boi_MC:x914 | boi_RP:x24 | boi_SE:x16 | N/A | N/A | N/A |
| 16.1 | Total public non performing assets/Commercial | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x1081 | boi_MC:x914 | boi_RP:x24 | boi_SE:x4 | N/A | boi_ST:x3 | N/A |
| 16.2 | Total public non performing assets/Housing | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x1081 | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| 16.3 | Total public non performing assets/Other private | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x1081 | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| 16.4 | Total public non performing assets/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x1081 | boi_MC:x914 | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x3 | N/A |