| r0.1 | label_boi_a2/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | N/A | boi_CS:x2 | N/A | boi_MC:x8 | N/A | N/A | boi_RP:x24 |
| r0.2 | label_boi_a2/Of which: bullet and balloon | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | N/A | boi_CS:x2 | N/A | boi_MC:x8 | boi_PI:x24 | N/A | boi_RP:x24 |
| r0.3 | label_boi_a2/Of which: variable rate | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | N/A | boi_CS:x2 | boi_CU:x24 | boi_MC:x8 | N/A | N/A | boi_RP:x24 |
| r0.4 | label_boi_a2/Total off-balance sheet credit risk | boi_met:mi184 | xbrli:monetaryItemType | instant | N/A | boi_CL:x35 | N/A | boi_CS:x2 | N/A | N/A | N/A | N/A | boi_RP:x24 |
| r1.1 | First degree pledge/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | N/A | boi_MC:x8 | N/A | N/A | boi_RP:x24 |
| r1.2 | First degree pledge/Of which: bullet and balloon | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | N/A | boi_MC:x8 | boi_PI:x24 | N/A | boi_RP:x24 |
| r1.3 | First degree pledge/Of which: variable rate | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | boi_CU:x24 | boi_MC:x8 | N/A | N/A | boi_RP:x24 |
| r1.4 | First degree pledge/Total off-balance sheet credit risk | boi_met:mi184 | xbrli:monetaryItemType | instant | N/A | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | N/A | N/A | N/A | N/A | boi_RP:x24 |
| 1.1 | LTV up to 60%/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | N/A | boi_MC:x8 | N/A | boi_PI:x36 | boi_RP:x24 |
| 1.2 | LTV up to 60%/Of which: bullet and balloon | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | N/A | boi_MC:x8 | boi_PI:x24 | boi_PI:x36 | boi_RP:x24 |
| 1.3 | LTV up to 60%/Of which: variable rate | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | boi_CU:x24 | boi_MC:x8 | N/A | boi_PI:x36 | boi_RP:x24 |
| 1.4 | LTV up to 60%/Total off-balance sheet credit risk | boi_met:mi184 | xbrli:monetaryItemType | instant | N/A | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | N/A | N/A | N/A | boi_PI:x36 | boi_RP:x24 |
| 2.1 | over 60%/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | N/A | boi_MC:x8 | N/A | boi_PI:x37 | boi_RP:x24 |
| 2.2 | over 60%/Of which: bullet and balloon | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | N/A | boi_MC:x8 | boi_PI:x24 | boi_PI:x37 | boi_RP:x24 |
| 2.3 | over 60%/Of which: variable rate | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | boi_CU:x24 | boi_MC:x8 | N/A | boi_PI:x37 | boi_RP:x24 |
| 2.4 | over 60%/Total off-balance sheet credit risk | boi_met:mi184 | xbrli:monetaryItemType | instant | N/A | boi_CL:x35 | boi_CL:x29 | boi_CS:x2 | N/A | N/A | N/A | boi_PI:x37 | boi_RP:x24 |
| 3.1 | Secondary or no pledge/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x30 | boi_CS:x2 | N/A | boi_MC:x8 | N/A | N/A | boi_RP:x24 |
| 3.2 | Secondary or no pledge/Of which: bullet and balloon | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x30 | boi_CS:x2 | N/A | boi_MC:x8 | boi_PI:x24 | N/A | boi_RP:x24 |
| 3.3 | Secondary or no pledge/Of which: variable rate | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CL:x30 | boi_CS:x2 | boi_CU:x24 | boi_MC:x8 | N/A | N/A | boi_RP:x24 |
| 3.4 | Secondary or no pledge/Total off-balance sheet credit risk | boi_met:mi184 | xbrli:monetaryItemType | instant | N/A | boi_CL:x35 | boi_CL:x30 | boi_CS:x2 | N/A | N/A | N/A | N/A | boi_RP:x24 |
| 4.1 | Total/Total | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | N/A | boi_CS:x2 | N/A | boi_MC:x8 | N/A | N/A | boi_RP:x24 |
| 4.2 | Total/Of which: bullet and balloon | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | N/A | boi_CS:x2 | N/A | boi_MC:x8 | boi_PI:x24 | N/A | boi_RP:x24 |
| 4.3 | Total/Of which: variable rate | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | N/A | boi_CS:x2 | boi_CU:x24 | boi_MC:x8 | N/A | N/A | boi_RP:x24 |
| 4.4 | Total/Total off-balance sheet credit risk | boi_met:mi184 | xbrli:monetaryItemType | instant | N/A | boi_CL:x35 | N/A | boi_CS:x2 | N/A | N/A | N/A | N/A | boi_RP:x24 |