| r0.1 | label_boi_a2/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| r0.2 | label_boi_a2/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| r0.3 | label_boi_a2/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | boi_ST:x8 | boi_ST:x3 | N/A |
| r0.4 | label_boi_a2/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| r0.5 | label_boi_a2/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| r1.1 | Debts not guaranteed by banks/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| r1.2 | Debts not guaranteed by banks/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| r1.3 | Debts not guaranteed by banks/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | boi_ST:x8 | boi_ST:x3 | N/A |
| r1.4 | Debts not guaranteed by banks/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| r1.5 | Debts not guaranteed by banks/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| r2.1 | Private individuals/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x6 | boi_ST:x3 | N/A |
| r2.2 | Private individuals/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x6 | boi_ST:x3 | N/A |
| r2.3 | Private individuals/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | boi_ST:x8 | boi_ST:x3 | N/A |
| r2.4 | Private individuals/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| r2.5 | Private individuals/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| 1.1 | Receivables in respect of credit cards/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | 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:x6 | boi_ST:x3 | N/A |
| 1.2 | Receivables in respect of credit cards/Balance of individual allowance | boi_met:mi3 | 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:x6 | boi_ST:x3 | N/A |
| 1.3 | Receivables in respect of credit cards/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | 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:x8 | boi_ST:x3 | N/A |
| 1.4 | Receivables in respect of credit cards/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | N/A | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| 1.5 | Receivables in respect of credit cards/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | N/A | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| 2.1 | Credit/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | 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:x6 | boi_ST:x3 | N/A |
| 2.2 | Credit/Balance of individual allowance | boi_met:mi3 | 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:x6 | boi_ST:x3 | N/A |
| 2.3 | Credit/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | 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:x8 | boi_ST:x3 | N/A |
| 2.4 | Credit/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | N/A | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| 2.5 | Credit/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | N/A | boi_RP:x24 | boi_SE:x15 | N/A | boi_ST:x3 | N/A |
| r5.1 | Commercial/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x6 | boi_ST:x3 | N/A |
| r5.2 | Commercial/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x6 | boi_ST:x3 | N/A |
| r5.3 | Commercial/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x4 | boi_ST:x8 | boi_ST:x3 | N/A |
| r5.4 | Commercial/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x4 | N/A | boi_ST:x3 | N/A |
| r5.5 | Commercial/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | N/A | N/A | boi_RP:x24 | boi_SE:x4 | N/A | boi_ST:x3 | N/A |
| 3.1 | Receivables in respect of credit cards/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | 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:x6 | boi_ST:x3 | N/A |
| 3.2 | Receivables in respect of credit cards/Balance of individual allowance | boi_met:mi3 | 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:x6 | boi_ST:x3 | N/A |
| 3.3 | Receivables in respect of credit cards/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | 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:x8 | boi_ST:x3 | N/A |
| 3.4 | Receivables in respect of credit cards/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | N/A | boi_RP:x24 | boi_SE:x4 | N/A | boi_ST:x3 | N/A |
| 3.5 | Receivables in respect of credit cards/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x143 | N/A | boi_RP:x24 | boi_SE:x4 | N/A | boi_ST:x3 | N/A |
| 4.1 | Credit/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | 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:x6 | boi_ST:x3 | N/A |
| 4.2 | Credit/Balance of individual allowance | boi_met:mi3 | 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:x6 | boi_ST:x3 | N/A |
| 4.3 | Credit/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | 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:x8 | boi_ST:x3 | N/A |
| 4.4 | Credit/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | N/A | boi_RP:x24 | boi_SE:x4 | N/A | boi_ST:x3 | N/A |
| 4.5 | Credit/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x880 | N/A | boi_RP:x24 | boi_SE:x4 | N/A | boi_ST:x3 | N/A |
| 5.1 | Total debts not guaranteed by banks/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| 5.2 | Total debts not guaranteed by banks/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| 5.3 | Total debts not guaranteed by banks/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x8 | boi_ST:x3 | N/A |
| 5.4 | Total debts not guaranteed by banks/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| 5.5 | Total debts not guaranteed by banks/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x2 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| 6.1 | Debts guaranteed by banks and others/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| 6.2 | Debts guaranteed by banks and others/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| 6.3 | Debts guaranteed by banks and others/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x8 | boi_ST:x3 | N/A |
| 6.4 | Debts guaranteed by banks and others/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| 6.5 | Debts guaranteed by banks and others/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x40 | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| 7.1 | Total/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| 7.2 | Total/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| 7.3 | Total/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x8 | boi_ST:x3 | N/A |
| 7.4 | Total/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| 7.5 | Total/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| 8.1 | Of which: Measured according to present value of cash flow/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | boi_PL:x6 | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| 8.2 | Of which: Measured according to present value of cash flow/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | boi_PL:x6 | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | N/A |
| 8.3 | Of which: Measured according to present value of cash flow/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | boi_PL:x6 | boi_RP:x24 | N/A | boi_ST:x8 | boi_ST:x3 | N/A |
| 8.4 | Of which: Measured according to present value of cash flow/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | boi_PL:x6 | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| 8.5 | Of which: Measured according to present value of cash flow/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | boi_PL:x6 | boi_RP:x24 | N/A | N/A | boi_ST:x3 | N/A |
| 9.1 | Of which: Debts under rescheduling of problem debts/Balance of impaired debts for which individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | boi_ST:x25 |
| 9.2 | Of which: Debts under rescheduling of problem debts/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x6 | boi_ST:x3 | boi_ST:x25 |
| 9.3 | Of which: Debts under rescheduling of problem debts/Balanceof impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | boi_ST:x8 | boi_ST:x3 | boi_ST:x25 |
| 9.4 | Of which: Debts under rescheduling of problem debts/Total balance of impaired debts | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | boi_ST:x25 |
| 9.5 | Of which: Debts under rescheduling of problem debts/Contractual balance of principal of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x8 | N/A | boi_RP:x24 | N/A | N/A | boi_ST:x3 | boi_ST:x25 |