| r0.1 | label_boi_a2/Commercial | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x25 | N/A | 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:x25 | N/A | 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:x25 | N/A | 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:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r0.5 | label_boi_a2/Banks and governments | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r0.6 | label_boi_a2/Total | | | | N/A | N/A | boi_CS:x2 | N/A | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r0.7 | label_boi_a2/Commercial | | | | N/A | N/A | boi_CS:x1 | N/A | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r0.8 | label_boi_a2/Housing | | | | N/A | boi_CL:x35 | boi_CS:x1 | N/A | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r0.9 | label_boi_a2/Other private | | | | N/A | boi_CL:x38 | boi_CS:x1 | N/A | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r0.10 | label_boi_a2/Total | | | | N/A | N/A | boi_CS:x1 | N/A | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r0.11 | label_boi_a2/Banks and governments | | | | N/A | N/A | boi_CS:x1 | N/A | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r0.12 | label_boi_a2/Total | | | | N/A | N/A | boi_CS:x1 | N/A | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r1.1 | Changes in balance of credit loss allowance/Commercial | | | | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r1.2 | Changes in balance of credit loss allowance/Housing | | | | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r1.3 | Changes in balance of credit loss allowance/Other private | | | | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r1.4 | Changes in balance of credit loss allowance/Total | | | | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r1.5 | Changes in balance of credit loss allowance/Banks and governments | | | | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r1.6 | Changes in balance of credit loss allowance/Total | | | | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r1.7 | Changes in balance of credit loss allowance/Commercial | | | | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r1.8 | Changes in balance of credit loss allowance/Housing | | | | boi_BC:x28 | boi_CL:x35 | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r1.9 | Changes in balance of credit loss allowance/Other private | | | | boi_BC:x28 | boi_CL:x38 | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r1.10 | Changes in balance of credit loss allowance/Total | | | | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r1.11 | Changes in balance of credit loss allowance/Banks and governments | | | | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r1.12 | Changes in balance of credit loss allowance/Total | | | | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 1.1 | Balance of allowance at start of period/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x4 | N/A | N/A | N/A |
| 1.2 | Balance of allowance at start of period/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x15 | N/A | N/A | N/A |
| 1.3 | Balance of allowance at start of period/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x15 | N/A | N/A | N/A |
| 1.4 | Balance of allowance at start of period/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x16 | N/A | N/A | N/A |
| 1.5 | Balance of allowance at start of period/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x77 | N/A | N/A | N/A |
| 1.6 | Balance of allowance at start of period/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | N/A | N/A | N/A | N/A |
| 1.7 | Balance of allowance at start of period/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x4 | N/A | N/A | N/A |
| 1.8 | Balance of allowance at start of period/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x15 | N/A | N/A | N/A |
| 1.9 | Balance of allowance at start of period/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x15 | N/A | N/A | N/A |
| 1.10 | Balance of allowance at start of period/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x16 | N/A | N/A | N/A |
| 1.11 | Balance of allowance at start of period/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | boi_SE:x77 | N/A | N/A | N/A |
| 1.12 | Balance of allowance at start of period/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | boi_RP:x22 | N/A | N/A | N/A | N/A |
| 2.1 | Expenses in respect to credit losses/Commercial | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 2.2 | Expenses in respect to credit losses/Housing | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 2.3 | Expenses in respect to credit losses/Other private | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 2.4 | Expenses in respect to credit losses/Total | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 2.5 | Expenses in respect to credit losses/Banks and governments | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 2.6 | Expenses in respect to credit losses/Total | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 2.7 | Expenses in respect to credit losses/Commercial | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 2.8 | Expenses in respect to credit losses/Housing | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 2.9 | Expenses in respect to credit losses/Other private | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 2.10 | Expenses in respect to credit losses/Total | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 2.11 | Expenses in respect to credit losses/Banks and governments | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 2.12 | Expenses in respect to credit losses/Total | boi_met:md191 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 3.1 | Accounting write-offs/Commercial | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 3.2 | Accounting write-offs/Housing | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 3.3 | Accounting write-offs/Other private | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 3.4 | Accounting write-offs/Total | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 3.5 | Accounting write-offs/Banks and governments | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 3.6 | Accounting write-offs/Total | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 3.7 | Accounting write-offs/Commercial | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 3.8 | Accounting write-offs/Housing | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 3.9 | Accounting write-offs/Other private | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 3.10 | Accounting write-offs/Total | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 3.11 | Accounting write-offs/Banks and governments | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 3.12 | Accounting write-offs/Total | boi_met:md193 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 4.1 | Collection of debts written-off in previous years/Commercial | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 4.2 | Collection of debts written-off in previous years/Housing | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 4.3 | Collection of debts written-off in previous years/Other private | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 4.4 | Collection of debts written-off in previous years/Total | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 4.5 | Collection of debts written-off in previous years/Banks and governments | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 4.6 | Collection of debts written-off in previous years/Total | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 4.7 | Collection of debts written-off in previous years/Commercial | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 4.8 | Collection of debts written-off in previous years/Housing | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 4.9 | Collection of debts written-off in previous years/Other private | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 4.10 | Collection of debts written-off in previous years/Total | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 4.11 | Collection of debts written-off in previous years/Banks and governments | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 4.12 | Collection of debts written-off in previous years/Total | boi_met:md192 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 5.1 | Net accounting write-offs/Commercial | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 5.2 | Net accounting write-offs/Housing | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 5.3 | Net accounting write-offs/Other private | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 5.4 | Net accounting write-offs/Total | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 5.5 | Net accounting write-offs/Banks and governments | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 5.6 | Net accounting write-offs/Total | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 5.7 | Net accounting write-offs/Commercial | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 5.8 | Net accounting write-offs/Housing | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 5.9 | Net accounting write-offs/Other private | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 5.10 | Net accounting write-offs/Total | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 5.11 | Net accounting write-offs/Banks and governments | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 5.12 | Net accounting write-offs/Total | boi_met:md285 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 6.1 | Adjustments from translation of financial statements/Commercial | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 6.2 | Adjustments from translation of financial statements/Housing | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 6.3 | Adjustments from translation of financial statements/Other private | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 6.4 | Adjustments from translation of financial statements/Total | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 6.5 | Adjustments from translation of financial statements/Banks and governments | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 6.6 | Adjustments from translation of financial statements/Total | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 6.7 | Adjustments from translation of financial statements/Commercial | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 6.8 | Adjustments from translation of financial statements/Housing | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 6.9 | Adjustments from translation of financial statements/Other private | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 6.10 | Adjustments from translation of financial statements/Total | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 6.11 | Adjustments from translation of financial statements/Banks and governments | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 6.12 | Adjustments from translation of financial statements/Total | boi_met:md194 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 7.1 | Other/Commercial | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 7.2 | Other/Housing | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 7.3 | Other/Other private | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 7.4 | Other/Total | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 7.5 | Other/Banks and governments | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 7.6 | Other/Total | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 7.7 | Other/Commercial | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 7.8 | Other/Housing | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 7.9 | Other/Other private | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 7.10 | Other/Total | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 7.11 | Other/Banks and governments | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 7.12 | Other/Total | boi_met:md195 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | boi_MU:x1 | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 8.1 | Balance of dredit loss allowance at the end of the year/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 8.2 | Balance of dredit loss allowance at the end of the year/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 8.3 | Balance of dredit loss allowance at the end of the year/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 8.4 | Balance of dredit loss allowance at the end of the year/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 8.5 | Balance of dredit loss allowance at the end of the year/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 8.6 | Balance of dredit loss allowance at the end of the year/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x2 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 8.7 | Balance of dredit loss allowance at the end of the year/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 8.8 | Balance of dredit loss allowance at the end of the year/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x35 | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 8.9 | Balance of dredit loss allowance at the end of the year/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | boi_CL:x38 | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 8.10 | Balance of dredit loss allowance at the end of the year/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 8.11 | Balance of dredit loss allowance at the end of the year/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 8.12 | Balance of dredit loss allowance at the end of the year/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x28 | N/A | boi_CS:x1 | boi_MC:x878 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 9.1 | Of which: in respect of off-balance sheet credit instruments/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x2 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 9.2 | Of which: in respect of off-balance sheet credit instruments/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CL:x35 | boi_CS:x2 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 9.3 | Of which: in respect of off-balance sheet credit instruments/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CL:x38 | boi_CS:x2 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 9.4 | Of which: in respect of off-balance sheet credit instruments/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x2 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 9.5 | Of which: in respect of off-balance sheet credit instruments/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x2 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 9.6 | Of which: in respect of off-balance sheet credit instruments/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x2 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 9.7 | Of which: in respect of off-balance sheet credit instruments/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x1 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 9.8 | Of which: in respect of off-balance sheet credit instruments/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CL:x35 | boi_CS:x1 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 9.9 | Of which: in respect of off-balance sheet credit instruments/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CL:x38 | boi_CS:x1 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 9.10 | Of which: in respect of off-balance sheet credit instruments/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x1 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 9.11 | Of which: in respect of off-balance sheet credit instruments/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x1 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 9.12 | Of which: in respect of off-balance sheet credit instruments/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | boi_CS:x1 | boi_MC:x879 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r11.1 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Commercial | | | | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r11.2 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Housing | | | | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r11.3 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Other private | | | | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r11.4 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Total | | | | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r11.5 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Banks and governments | | | | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r11.6 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Total | | | | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r11.7 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Commercial | | | | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r11.8 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Housing | | | | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r11.9 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Other private | | | | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r11.10 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Total | | | | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r11.11 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Banks and governments | | | | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r11.12 | Additional information on the method of calculating the credit loss allowance in respect of debts and on debts on which it was calculated/Total | | | | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r12.1 | Recorded debt balance of debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r12.2 | Recorded debt balance of debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r12.3 | Recorded debt balance of debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r12.4 | Recorded debt balance of debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r12.5 | Recorded debt balance of debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r12.6 | Recorded debt balance of debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r12.7 | Recorded debt balance of debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r12.8 | Recorded debt balance of debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r12.9 | Recorded debt balance of debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r12.10 | Recorded debt balance of debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r12.11 | Recorded debt balance of debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r12.12 | Recorded debt balance of debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 10.1 | Examined on individual basis/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x28 | N/A | N/A |
| 10.2 | Examined on individual basis/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x28 | N/A | N/A |
| 10.3 | Examined on individual basis/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x28 | N/A | N/A |
| 10.4 | Examined on individual basis/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x28 | N/A | N/A |
| 10.5 | Examined on individual basis/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x28 | N/A | N/A |
| 10.6 | Examined on individual basis/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x28 | N/A | N/A |
| 10.7 | Examined on individual basis/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x28 | N/A | N/A |
| 10.8 | Examined on individual basis/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x28 | N/A | N/A |
| 10.9 | Examined on individual basis/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x28 | N/A | N/A |
| 10.10 | Examined on individual basis/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x28 | N/A | N/A |
| 10.11 | Examined on individual basis/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x28 | N/A | N/A |
| 10.12 | Examined on individual basis/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x28 | N/A | N/A |
| 11.1 | Examined oncollective basis/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x29 | N/A | N/A |
| 11.2 | Examined oncollective basis/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x29 | N/A | N/A |
| 11.3 | Examined oncollective basis/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x29 | N/A | N/A |
| 11.4 | Examined oncollective basis/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x29 | N/A | N/A |
| 11.5 | Examined oncollective basis/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x29 | N/A | N/A |
| 11.6 | Examined oncollective basis/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x29 | N/A | N/A |
| 11.7 | Examined oncollective basis/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x29 | N/A | N/A |
| 11.8 | Examined oncollective basis/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x29 | N/A | N/A |
| 11.9 | Examined oncollective basis/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x29 | N/A | N/A |
| 11.10 | Examined oncollective basis/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x29 | N/A | N/A |
| 11.11 | Examined oncollective basis/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x29 | N/A | N/A |
| 11.12 | Examined oncollective basis/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x29 | N/A | N/A |
| 12.1 | Of which: the allowance was calculated by extent of arrears/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x33 | N/A | N/A |
| 12.2 | Of which: the allowance was calculated by extent of arrears/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x33 | N/A | N/A |
| 12.3 | Of which: the allowance was calculated by extent of arrears/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x33 | N/A | N/A |
| 12.4 | Of which: the allowance was calculated by extent of arrears/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x33 | N/A | N/A |
| 12.5 | Of which: the allowance was calculated by extent of arrears/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x33 | N/A | N/A |
| 12.6 | Of which: the allowance was calculated by extent of arrears/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x33 | N/A | N/A |
| 12.7 | Of which: the allowance was calculated by extent of arrears/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x33 | N/A | N/A |
| 12.8 | Of which: the allowance was calculated by extent of arrears/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x33 | N/A | N/A |
| 12.9 | Of which: the allowance was calculated by extent of arrears/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x33 | N/A | N/A |
| 12.10 | Of which: the allowance was calculated by extent of arrears/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x33 | N/A | N/A |
| 12.11 | Of which: the allowance was calculated by extent of arrears/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x33 | N/A | N/A |
| 12.12 | Of which: the allowance was calculated by extent of arrears/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x33 | N/A | N/A |
| 13.1 | Total debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 13.2 | Total debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 13.3 | Total debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 13.4 | Total debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 13.5 | Total debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 13.6 | Total debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 13.7 | Total debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 13.8 | Total debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 13.9 | Total debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 13.10 | Total debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 13.11 | Total debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 13.12 | Total debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r17.1 | Of which:/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r17.2 | Of which:/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r17.3 | Of which:/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r17.4 | Of which:/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r17.5 | Of which:/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r17.6 | Of which:/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r17.7 | Of which:/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r17.8 | Of which:/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r17.9 | Of which:/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r17.10 | Of which:/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r17.11 | Of which:/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r17.12 | Of which:/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 14.1 | Recycled debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.2 | Recycled debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.3 | Recycled debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.4 | Recycled debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.5 | Recycled debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.6 | Recycled debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.7 | Recycled debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.8 | Recycled debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.9 | Recycled debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.10 | Recycled debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.11 | Recycled debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x3 | boi_ST:x25 | N/A |
| 14.12 | Recycled debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x3 | boi_ST:x25 | N/A |
| 15.1 | Other impaired debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | boi_ST:x152 | N/A |
| 15.2 | Other impaired debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | boi_ST:x152 | N/A |
| 15.3 | Other impaired debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | boi_ST:x152 | N/A |
| 15.4 | Other impaired debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | boi_ST:x152 | N/A |
| 15.5 | Other impaired debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | boi_ST:x152 | N/A |
| 15.6 | Other impaired debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | boi_ST:x152 | N/A |
| 15.7 | Other impaired debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | boi_ST:x152 | N/A |
| 15.8 | Other impaired debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | boi_ST:x152 | N/A |
| 15.9 | Other impaired debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | boi_ST:x152 | N/A |
| 15.10 | Other impaired debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | boi_ST:x152 | N/A |
| 15.11 | Other impaired debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | boi_ST:x152 | N/A |
| 15.12 | Other impaired debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | boi_ST:x152 | N/A |
| 16.1 | Total impaired debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x3 | N/A | N/A |
| 16.2 | Total impaired debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | N/A | N/A |
| 16.3 | Total impaired debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | N/A | N/A |
| 16.4 | Total impaired debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x3 | N/A | N/A |
| 16.5 | Total impaired debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x3 | N/A | N/A |
| 16.6 | Total impaired debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x3 | N/A | N/A |
| 16.7 | Total impaired debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x3 | N/A | N/A |
| 16.8 | Total impaired debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | N/A | N/A |
| 16.9 | Total impaired debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | N/A | N/A |
| 16.10 | Total impaired debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x3 | N/A | N/A |
| 16.11 | Total impaired debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x3 | N/A | N/A |
| 16.12 | Total impaired debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x3 | N/A | N/A |
| 17.1 | Problematic debts 90 days and more/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.2 | Problematic debts 90 days and more/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.3 | Problematic debts 90 days and more/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.4 | Problematic debts 90 days and more/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.5 | Problematic debts 90 days and more/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.6 | Problematic debts 90 days and more/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.7 | Problematic debts 90 days and more/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.8 | Problematic debts 90 days and more/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.9 | Problematic debts 90 days and more/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.10 | Problematic debts 90 days and more/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.11 | Problematic debts 90 days and more/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x4 | N/A | boi_TI:x2 |
| 17.12 | Problematic debts 90 days and more/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x4 | N/A | boi_TI:x2 |
| 18.1 | Other problematic debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.2 | Other problematic debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.3 | Other problematic debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.4 | Other problematic debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.5 | Other problematic debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.6 | Other problematic debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.7 | Other problematic debts/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.8 | Other problematic debts/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.9 | Other problematic debts/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.10 | Other problematic debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.11 | Other problematic debts/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x4 | N/A | boi_TI:x94 |
| 18.12 | Other problematic debts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x4 | N/A | boi_TI:x94 |
| 19.1 | Problem debts - not impaired/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x2 | N/A | N/A |
| 19.2 | Problem debts - not impaired/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x2 | N/A | N/A |
| 19.3 | Problem debts - not impaired/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x2 | N/A | N/A |
| 19.4 | Problem debts - not impaired/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x2 | N/A | N/A |
| 19.5 | Problem debts - not impaired/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x2 | N/A | N/A |
| 19.6 | Problem debts - not impaired/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x2 | N/A | N/A |
| 19.7 | Problem debts - not impaired/Commercial | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x2 | N/A | N/A |
| 19.8 | Problem debts - not impaired/Housing | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x2 | N/A | N/A |
| 19.9 | Problem debts - not impaired/Other private | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x2 | N/A | N/A |
| 19.10 | Problem debts - not impaired/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x2 | N/A | N/A |
| 19.11 | Problem debts - not impaired/Banks and governments | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x2 | N/A | N/A |
| 19.12 | Problem debts - not impaired/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x2 | N/A | N/A |
| r24.1 | Credit loss allowance by debts/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r24.2 | Credit loss allowance by debts/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r24.3 | Credit loss allowance by debts/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r24.4 | Credit loss allowance by debts/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r24.5 | Credit loss allowance by debts/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r24.6 | Credit loss allowance by debts/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| r24.7 | Credit loss allowance by debts/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| r24.8 | Credit loss allowance by debts/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r24.9 | Credit loss allowance by debts/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| r24.10 | Credit loss allowance by debts/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| r24.11 | Credit loss allowance by debts/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| r24.12 | Credit loss allowance by debts/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 20.1 | Examined on individual basis/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x28 | N/A | N/A |
| 20.2 | Examined on individual basis/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x28 | N/A | N/A |
| 20.3 | Examined on individual basis/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x28 | N/A | N/A |
| 20.4 | Examined on individual basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x28 | N/A | N/A |
| 20.5 | Examined on individual basis/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x28 | N/A | N/A |
| 20.6 | Examined on individual basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x28 | N/A | N/A |
| 20.7 | Examined on individual basis/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x28 | N/A | N/A |
| 20.8 | Examined on individual basis/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x28 | N/A | N/A |
| 20.9 | Examined on individual basis/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x28 | N/A | N/A |
| 20.10 | Examined on individual basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x28 | N/A | N/A |
| 20.11 | Examined on individual basis/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x28 | N/A | N/A |
| 20.12 | Examined on individual basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x28 | N/A | N/A |
| 21.1 | Examined oncollective basis/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x29 | N/A | N/A |
| 21.2 | Examined oncollective basis/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x29 | N/A | N/A |
| 21.3 | Examined oncollective basis/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x29 | N/A | N/A |
| 21.4 | Examined oncollective basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x29 | N/A | N/A |
| 21.5 | Examined oncollective basis/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x29 | N/A | N/A |
| 21.6 | Examined oncollective basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x29 | N/A | N/A |
| 21.7 | Examined oncollective basis/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x29 | N/A | N/A |
| 21.8 | Examined oncollective basis/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x29 | N/A | N/A |
| 21.9 | Examined oncollective basis/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x29 | N/A | N/A |
| 21.10 | Examined oncollective basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x29 | N/A | N/A |
| 21.11 | Examined oncollective basis/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x29 | N/A | N/A |
| 21.12 | Examined oncollective basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x29 | N/A | N/A |
| 22.1 | Of which: the allowance was calculated by extent of arrears/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x33 | N/A | N/A |
| 22.2 | Of which: the allowance was calculated by extent of arrears/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x33 | N/A | N/A |
| 22.3 | Of which: the allowance was calculated by extent of arrears/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x33 | N/A | N/A |
| 22.4 | Of which: the allowance was calculated by extent of arrears/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x33 | N/A | N/A |
| 22.5 | Of which: the allowance was calculated by extent of arrears/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x33 | N/A | N/A |
| 22.6 | Of which: the allowance was calculated by extent of arrears/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x33 | N/A | N/A |
| 22.7 | Of which: the allowance was calculated by extent of arrears/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x33 | N/A | N/A |
| 22.8 | Of which: the allowance was calculated by extent of arrears/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x33 | N/A | N/A |
| 22.9 | Of which: the allowance was calculated by extent of arrears/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x33 | N/A | N/A |
| 22.10 | Of which: the allowance was calculated by extent of arrears/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x33 | N/A | N/A |
| 22.11 | Of which: the allowance was calculated by extent of arrears/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x33 | N/A | N/A |
| 22.12 | Of which: the allowance was calculated by extent of arrears/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x33 | N/A | N/A |
| 23.1 | Including allowance beyond requirements calculated on individual basis/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x34 | N/A | N/A |
| 23.2 | Including allowance beyond requirements calculated on individual basis/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x34 | N/A | N/A |
| 23.3 | Including allowance beyond requirements calculated on individual basis/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x34 | N/A | N/A |
| 23.4 | Including allowance beyond requirements calculated on individual basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x34 | N/A | N/A |
| 23.5 | Including allowance beyond requirements calculated on individual basis/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x34 | N/A | N/A |
| 23.6 | Including allowance beyond requirements calculated on individual basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x34 | N/A | N/A |
| 23.7 | Including allowance beyond requirements calculated on individual basis/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x34 | N/A | N/A |
| 23.8 | Including allowance beyond requirements calculated on individual basis/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x34 | N/A | N/A |
| 23.9 | Including allowance beyond requirements calculated on individual basis/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x34 | N/A | N/A |
| 23.10 | Including allowance beyond requirements calculated on individual basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x34 | N/A | N/A |
| 23.11 | Including allowance beyond requirements calculated on individual basis/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x34 | N/A | N/A |
| 23.12 | Including allowance beyond requirements calculated on individual basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x34 | N/A | N/A |
| 24.1 | Including allowance beyond requirements calculated on collective basis/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x35 | N/A | N/A |
| 24.2 | Including allowance beyond requirements calculated on collective basis/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x35 | N/A | N/A |
| 24.3 | Including allowance beyond requirements calculated on collective basis/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x35 | N/A | N/A |
| 24.4 | Including allowance beyond requirements calculated on collective basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x35 | N/A | N/A |
| 24.5 | Including allowance beyond requirements calculated on collective basis/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x35 | N/A | N/A |
| 24.6 | Including allowance beyond requirements calculated on collective basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x35 | N/A | N/A |
| 24.7 | Including allowance beyond requirements calculated on collective basis/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x35 | N/A | N/A |
| 24.8 | Including allowance beyond requirements calculated on collective basis/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x35 | N/A | N/A |
| 24.9 | Including allowance beyond requirements calculated on collective basis/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x35 | N/A | N/A |
| 24.10 | Including allowance beyond requirements calculated on collective basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x35 | N/A | N/A |
| 24.11 | Including allowance beyond requirements calculated on collective basis/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x35 | N/A | N/A |
| 24.12 | Including allowance beyond requirements calculated on collective basis/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x35 | N/A | N/A |
| 25.1 | Total allowance for credit losses/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 25.2 | Total allowance for credit losses/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 25.3 | Total allowance for credit losses/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 25.4 | Total allowance for credit losses/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 25.5 | Total allowance for credit losses/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 25.6 | Total allowance for credit losses/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 25.7 | Total allowance for credit losses/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | N/A | N/A | N/A |
| 25.8 | Total allowance for credit losses/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 25.9 | Total allowance for credit losses/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | N/A | N/A | N/A |
| 25.10 | Total allowance for credit losses/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | N/A | N/A | N/A |
| 25.11 | Total allowance for credit losses/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | N/A | N/A | N/A |
| 25.12 | Total allowance for credit losses/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | N/A | N/A | N/A |
| 26.1 | of which: for impaired debts/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x3 | N/A | N/A |
| 26.2 | of which: for impaired debts/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | N/A | N/A |
| 26.3 | of which: for impaired debts/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | N/A | N/A |
| 26.4 | of which: for impaired debts/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x3 | N/A | N/A |
| 26.5 | of which: for impaired debts/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x3 | N/A | N/A |
| 26.6 | of which: for impaired debts/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x3 | N/A | N/A |
| 26.7 | of which: for impaired debts/Commercial | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x4 | boi_ST:x3 | N/A | N/A |
| 26.8 | of which: for impaired debts/Housing | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | N/A | N/A |
| 26.9 | of which: for impaired debts/Other private | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x38 | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x15 | boi_ST:x3 | N/A | N/A |
| 26.10 | of which: for impaired debts/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x16 | boi_ST:x3 | N/A | N/A |
| 26.11 | of which: for impaired debts/Banks and governments | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | boi_SE:x77 | boi_ST:x3 | N/A | N/A |
| 26.12 | of which: for impaired debts/Total | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x1 | boi_MC:x640 | N/A | boi_RP:x25 | N/A | N/A | boi_ST:x3 | N/A | N/A |