| r0.1 | label_boi_a2/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_MC:x914 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| r0.2 | label_boi_a2/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| r0.3 | label_boi_a2/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| r0.4 | label_boi_a2/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| r0.5 | label_boi_a2/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| r1.1 | Debts not guaranteed by banks/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x914 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| r1.2 | Debts not guaranteed by banks/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| r1.3 | Debts not guaranteed by banks/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| r1.4 | Debts not guaranteed by banks/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| r1.5 | Debts not guaranteed by banks/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| r2.1 | Private individuals/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| r2.2 | Private individuals/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| r2.3 | Private individuals/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| r2.4 | Private individuals/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| r2.5 | Private individuals/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| 1.1 | Receivables in respect of credit cards/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| 1.2 | Receivables in respect of credit cards/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | boi_MC:x962 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| 1.3 | Receivables in respect of credit cards/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | boi_MC:x962 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| 1.4 | Receivables in respect of credit cards/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | boi_MC:x962 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| 1.5 | Receivables in respect of credit cards/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| 2.1 | Credit 4/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | boi_MC:x914 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| 2.2 | Credit 4/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | boi_MC:x962 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| 2.3 | Credit 4/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | boi_MC:x962 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| 2.4 | Credit 4/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | boi_MC:x962 | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| 2.5 | Credit 4/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| r5.1 | Commercial/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x914 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | N/A |
| r5.2 | Commercial/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| r5.3 | Commercial/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| r5.4 | Commercial/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | boi_MC:x962 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| r5.5 | Commercial/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | N/A |
| 3.1 | Receivables in respect of credit cards/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | boi_MC:x914 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | N/A |
| 3.2 | Receivables in respect of credit cards/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | boi_MC:x962 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| 3.3 | Receivables in respect of credit cards/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | boi_MC:x962 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| 3.4 | Receivables in respect of credit cards/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | boi_MC:x962 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| 3.5 | Receivables in respect of credit cards/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | N/A |
| 4.1 | Credit 5/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | boi_MC:x914 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | N/A |
| 4.2 | Credit 5/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | boi_MC:x962 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| 4.3 | Credit 5/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | boi_MC:x962 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| 4.4 | Credit 5/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | boi_MC:x962 | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| 4.5 | Credit 5/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | N/A |
| 5.1 | Total debts not guaranteed by banks/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | boi_MC:x914 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| 5.2 | Total debts not guaranteed by banks/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| 5.3 | Total debts not guaranteed by banks/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| 5.4 | Total debts not guaranteed by banks/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| 5.5 | Total debts not guaranteed by banks/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| 6.1 | Debts guaranteed by banks and others/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | boi_MC:x914 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| 6.2 | Debts guaranteed by banks and others/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| 6.3 | Debts guaranteed by banks and others/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| 6.4 | Debts guaranteed by banks and others/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| 6.5 | Debts guaranteed by banks and others/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| 7.1 | Total/Not accruing interest income | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | boi_MC:x914 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| 7.2 | Total/Accruing, in arrears of 90 days or more | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x2 |
| 7.3 | Total/Accruing, in arrears of 30 to 89 days | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x1 |
| 7.4 | Total/Accruing, not in arrears | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | boi_MC:x962 | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | boi_TI:x4 |
| 7.5 | Total/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x3 | boi_ST:x25 | N/A |