| r0.1 | label_boi_a2/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A |
| r0.2 | label_boi_a2/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A |
| r0.3 | label_boi_a2/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A |
| r0.4 | label_boi_a2/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A |
| r0.5 | label_boi_a2/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A |
| r0.6 | label_boi_a2/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A |
| r0.7 | label_boi_a2/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A |
| r0.8 | label_boi_a2/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A |
| r0.9 | label_boi_a2/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | N/A | N/A | N/A | N/A |
| 1.1 | Total of all exposures/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 1.2 | Total of all exposures/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 1.3 | Total of all exposures/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 1.4 | Total of all exposures/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 1.5 | Total of all exposures/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 1.6 | Total of all exposures/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 1.7 | Total of all exposures/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 1.8 | Total of all exposures/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 1.9 | Total of all exposures/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r2.1 | Investments of banking corporation/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r2.2 | Investments of banking corporation/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r2.3 | Investments of banking corporation/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r2.4 | Investments of banking corporation/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r2.5 | Investments of banking corporation/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r2.6 | Investments of banking corporation/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r2.7 | Investments of banking corporation/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r2.8 | Investments of banking corporation/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r2.9 | Investments of banking corporation/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r3.1 | Balance sheet exposure/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r3.2 | Balance sheet exposure/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r3.3 | Balance sheet exposure/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r3.4 | Balance sheet exposure/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r3.5 | Balance sheet exposure/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r3.6 | Balance sheet exposure/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r3.7 | Balance sheet exposure/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r3.8 | Balance sheet exposure/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| r3.9 | Balance sheet exposure/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x14 | boi_RT:x1 |
| 2.1 | Most senior/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x14 | boi_RT:x1 |
| 2.2 | Most senior/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x14 | boi_RT:x1 |
| 2.3 | Most senior/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x14 | boi_RT:x1 |
| 2.4 | Most senior/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x14 | boi_RT:x1 |
| 2.5 | Most senior/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x14 | boi_RT:x1 |
| 2.6 | Most senior/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x14 | boi_RT:x1 |
| 2.7 | Most senior/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x14 | boi_RT:x1 |
| 2.8 | Most senior/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x14 | boi_RT:x1 |
| 2.9 | Most senior/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x14 | boi_RT:x1 |
| 3.1 | Medium/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x14 | boi_RT:x1 |
| 3.2 | Medium/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x14 | boi_RT:x1 |
| 3.3 | Medium/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x14 | boi_RT:x1 |
| 3.4 | Medium/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x14 | boi_RT:x1 |
| 3.5 | Medium/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x14 | boi_RT:x1 |
| 3.6 | Medium/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x14 | boi_RT:x1 |
| 3.7 | Medium/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x14 | boi_RT:x1 |
| 3.8 | Medium/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x14 | boi_RT:x1 |
| 3.9 | Medium/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x14 | boi_RT:x1 |
| 4.1 | First loss/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x14 | boi_RT:x1 |
| 4.2 | First loss/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x14 | boi_RT:x1 |
| 4.3 | First loss/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x14 | boi_RT:x1 |
| 4.4 | First loss/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x14 | boi_RT:x1 |
| 4.5 | First loss/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x14 | boi_RT:x1 |
| 4.6 | First loss/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x14 | boi_RT:x1 |
| 4.7 | First loss/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x14 | boi_RT:x1 |
| 4.8 | First loss/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x14 | boi_RT:x1 |
| 4.9 | First loss/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x14 | boi_RT:x1 |
| 5.1 | Total/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x14 | boi_RT:x1 |
| 5.2 | Total/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x14 | boi_RT:x1 |
| 5.3 | Total/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x14 | boi_RT:x1 |
| 5.4 | Total/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x14 | boi_RT:x1 |
| 5.5 | Total/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x14 | boi_RT:x1 |
| 5.6 | Total/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x14 | boi_RT:x1 |
| 5.7 | Total/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x14 | boi_RT:x1 |
| 5.8 | Total/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x14 | boi_RT:x1 |
| 5.9 | Total/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x14 | boi_RT:x1 |
| 6.1 | Off balance sheet exposure/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x14 | boi_RT:x1 |
| 6.2 | Off balance sheet exposure/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x14 | boi_RT:x1 |
| 6.3 | Off balance sheet exposure/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x14 | boi_RT:x1 |
| 6.4 | Off balance sheet exposure/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x14 | boi_RT:x1 |
| 6.5 | Off balance sheet exposure/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x14 | boi_RT:x1 |
| 6.6 | Off balance sheet exposure/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x14 | boi_RT:x1 |
| 6.7 | Off balance sheet exposure/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x14 | boi_RT:x1 |
| 6.8 | Off balance sheet exposure/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x14 | boi_RT:x1 |
| 6.9 | Off balance sheet exposure/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x14 | boi_RT:x1 |
| 7.1 | Total/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x14 | boi_RT:x1 |
| 7.2 | Total/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x14 | boi_RT:x1 |
| 7.3 | Total/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x14 | boi_RT:x1 |
| 7.4 | Total/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x14 | boi_RT:x1 |
| 7.5 | Total/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x14 | boi_RT:x1 |
| 7.6 | Total/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x14 | boi_RT:x1 |
| 7.7 | Total/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x14 | boi_RT:x1 |
| 7.8 | Total/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x14 | boi_RT:x1 |
| 7.9 | Total/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x14 | boi_RT:x1 |
| r10.1 | B. With funding from banking corporation/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x15 | boi_RT:x1 |
| r10.2 | B. With funding from banking corporation/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x15 | boi_RT:x1 |
| r10.3 | B. With funding from banking corporation/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x15 | boi_RT:x1 |
| r10.4 | B. With funding from banking corporation/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x15 | boi_RT:x1 |
| r10.5 | B. With funding from banking corporation/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x15 | boi_RT:x1 |
| r10.6 | B. With funding from banking corporation/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x15 | boi_RT:x1 |
| r10.7 | B. With funding from banking corporation/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x15 | boi_RT:x1 |
| r10.8 | B. With funding from banking corporation/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x15 | boi_RT:x1 |
| r10.9 | B. With funding from banking corporation/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x15 | boi_RT:x1 |
| 8.1 | Balance sheet exposure/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x15 | boi_RT:x1 |
| 8.2 | Balance sheet exposure/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x15 | boi_RT:x1 |
| 8.3 | Balance sheet exposure/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x15 | boi_RT:x1 |
| 8.4 | Balance sheet exposure/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x15 | boi_RT:x1 |
| 8.5 | Balance sheet exposure/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x15 | boi_RT:x1 |
| 8.6 | Balance sheet exposure/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x15 | boi_RT:x1 |
| 8.7 | Balance sheet exposure/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x15 | boi_RT:x1 |
| 8.8 | Balance sheet exposure/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x15 | boi_RT:x1 |
| 8.9 | Balance sheet exposure/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x15 | boi_RT:x1 |
| 9.1 | Off balance sheet and derivative exposure/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x15 | boi_RT:x1 |
| 9.2 | Off balance sheet and derivative exposure/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x15 | boi_RT:x1 |
| 9.3 | Off balance sheet and derivative exposure/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x15 | boi_RT:x1 |
| 9.4 | Off balance sheet and derivative exposure/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x15 | boi_RT:x1 |
| 9.5 | Off balance sheet and derivative exposure/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x15 | boi_RT:x1 |
| 9.6 | Off balance sheet and derivative exposure/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x15 | boi_RT:x1 |
| 9.7 | Off balance sheet and derivative exposure/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x15 | boi_RT:x1 |
| 9.8 | Off balance sheet and derivative exposure/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x15 | boi_RT:x1 |
| 9.9 | Off balance sheet and derivative exposure/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x15 | boi_RT:x1 |
| 10.1 | Total/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x15 | boi_RT:x1 |
| 10.2 | Total/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x15 | boi_RT:x1 |
| 10.3 | Total/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x15 | boi_RT:x1 |
| 10.4 | Total/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x15 | boi_RT:x1 |
| 10.5 | Total/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x15 | boi_RT:x1 |
| 10.6 | Total/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x15 | boi_RT:x1 |
| 10.7 | Total/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x15 | boi_RT:x1 |
| 10.8 | Total/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x15 | boi_RT:x1 |
| 10.9 | Total/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x15 | boi_RT:x1 |
| r14.1 | C. At initiative of banking corporation/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | N/A |
| r14.2 | C. At initiative of banking corporation/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | N/A |
| r14.3 | C. At initiative of banking corporation/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | N/A |
| r14.4 | C. At initiative of banking corporation/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | N/A |
| r14.5 | C. At initiative of banking corporation/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | N/A |
| r14.6 | C. At initiative of banking corporation/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | N/A |
| r14.7 | C. At initiative of banking corporation/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | N/A |
| r14.8 | C. At initiative of banking corporation/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | N/A |
| r14.9 | C. At initiative of banking corporation/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | N/A |
| r15.1 | Balance sheet exposure/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | boi_RT:x23 |
| r15.2 | Balance sheet exposure/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | boi_RT:x23 |
| r15.3 | Balance sheet exposure/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | boi_RT:x23 |
| r15.4 | Balance sheet exposure/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | boi_RT:x23 |
| r15.5 | Balance sheet exposure/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | boi_RT:x23 |
| r15.6 | Balance sheet exposure/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | boi_RT:x23 |
| r15.7 | Balance sheet exposure/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | boi_RT:x23 |
| r15.8 | Balance sheet exposure/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | boi_RT:x23 |
| r15.9 | Balance sheet exposure/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | N/A | N/A | boi_PU:x16 | boi_RT:x23 |
| 11.1 | Most senior/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x16 | boi_RT:x23 |
| 11.2 | Most senior/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x16 | boi_RT:x23 |
| 11.3 | Most senior/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x16 | boi_RT:x23 |
| 11.4 | Most senior/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x16 | boi_RT:x23 |
| 11.5 | Most senior/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x16 | boi_RT:x23 |
| 11.6 | Most senior/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x16 | boi_RT:x23 |
| 11.7 | Most senior/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x16 | boi_RT:x23 |
| 11.8 | Most senior/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x16 | boi_RT:x23 |
| 11.9 | Most senior/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x849 | N/A | boi_PU:x16 | boi_RT:x23 |
| 12.1 | Medium/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x16 | boi_RT:x23 |
| 12.2 | Medium/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x16 | boi_RT:x23 |
| 12.3 | Medium/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x16 | boi_RT:x23 |
| 12.4 | Medium/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x16 | boi_RT:x23 |
| 12.5 | Medium/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x16 | boi_RT:x23 |
| 12.6 | Medium/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x16 | boi_RT:x23 |
| 12.7 | Medium/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x16 | boi_RT:x23 |
| 12.8 | Medium/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x16 | boi_RT:x23 |
| 12.9 | Medium/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x850 | N/A | boi_PU:x16 | boi_RT:x23 |
| 13.1 | First loss/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x16 | boi_RT:x23 |
| 13.2 | First loss/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x16 | boi_RT:x23 |
| 13.3 | First loss/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x16 | boi_RT:x23 |
| 13.4 | First loss/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x16 | boi_RT:x23 |
| 13.5 | First loss/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x16 | boi_RT:x23 |
| 13.6 | First loss/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x16 | boi_RT:x23 |
| 13.7 | First loss/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x16 | boi_RT:x23 |
| 13.8 | First loss/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x16 | boi_RT:x23 |
| 13.9 | First loss/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x851 | N/A | boi_PU:x16 | boi_RT:x23 |
| 14.1 | Total/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x16 | boi_RT:x23 |
| 14.2 | Total/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x16 | boi_RT:x23 |
| 14.3 | Total/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x16 | boi_RT:x23 |
| 14.4 | Total/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x16 | boi_RT:x23 |
| 14.5 | Total/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x16 | boi_RT:x23 |
| 14.6 | Total/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x16 | boi_RT:x23 |
| 14.7 | Total/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x16 | boi_RT:x23 |
| 14.8 | Total/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x16 | boi_RT:x23 |
| 14.9 | Total/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x848 | N/A | boi_PU:x16 | boi_RT:x23 |
| 15.1 | Off balance sheet exposure/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x16 | boi_RT:x23 |
| 15.2 | Off balance sheet exposure/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x16 | boi_RT:x23 |
| 15.3 | Off balance sheet exposure/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x16 | boi_RT:x23 |
| 15.4 | Off balance sheet exposure/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x16 | boi_RT:x23 |
| 15.5 | Off balance sheet exposure/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x16 | boi_RT:x23 |
| 15.6 | Off balance sheet exposure/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x16 | boi_RT:x23 |
| 15.7 | Off balance sheet exposure/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x16 | boi_RT:x23 |
| 15.8 | Off balance sheet exposure/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x16 | boi_RT:x23 |
| 15.9 | Off balance sheet exposure/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x852 | N/A | boi_PU:x16 | boi_RT:x23 |
| 16.1 | Early payback/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x22 |
| 16.2 | Early payback/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x22 |
| 16.3 | Early payback/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x22 |
| 16.4 | Early payback/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x22 |
| 16.5 | Early payback/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x22 |
| 16.6 | Early payback/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x22 |
| 16.7 | Early payback/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x22 |
| 16.8 | Early payback/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x22 |
| 16.9 | Early payback/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x22 |
| 17.1 | Total/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x1 |
| 17.2 | Total/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x1 |
| 17.3 | Total/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x1 |
| 17.4 | Total/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x1 |
| 17.5 | Total/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x1 |
| 17.6 | Total/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x1 |
| 17.7 | Total/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x1 |
| 17.8 | Total/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x1 |
| 17.9 | Total/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x10 | boi_MC:x250 | N/A | boi_PU:x16 | boi_RT:x1 |
| r23.1 | D. Breakdown of exposures by risk weights/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r23.2 | D. Breakdown of exposures by risk weights/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r23.3 | D. Breakdown of exposures by risk weights/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r23.4 | D. Breakdown of exposures by risk weights/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r23.5 | D. Breakdown of exposures by risk weights/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r23.6 | D. Breakdown of exposures by risk weights/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r23.7 | D. Breakdown of exposures by risk weights/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r23.8 | D. Breakdown of exposures by risk weights/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r23.9 | D. Breakdown of exposures by risk weights/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | N/A | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r24.1 | Securitization exposures/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r24.2 | Securitization exposures/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r24.3 | Securitization exposures/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r24.4 | Securitization exposures/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r24.5 | Securitization exposures/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r24.6 | Securitization exposures/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r24.7 | Securitization exposures/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r24.8 | Securitization exposures/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r24.9 | Securitization exposures/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 18.1 | 20%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x7 | N/A | boi_RT:x1 |
| 18.2 | 20%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x7 | N/A | boi_RT:x1 |
| 18.3 | 20%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x7 | N/A | boi_RT:x1 |
| 18.4 | 20%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x7 | N/A | boi_RT:x1 |
| 18.5 | 20%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x7 | N/A | boi_RT:x1 |
| 18.6 | 20%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x7 | N/A | boi_RT:x1 |
| 18.7 | 20%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x7 | N/A | boi_RT:x1 |
| 18.8 | 20%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x7 | N/A | boi_RT:x1 |
| 18.9 | 20%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x7 | N/A | boi_RT:x1 |
| 19.1 | 50%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x9 | N/A | boi_RT:x1 |
| 19.2 | 50%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x9 | N/A | boi_RT:x1 |
| 19.3 | 50%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x9 | N/A | boi_RT:x1 |
| 19.4 | 50%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x9 | N/A | boi_RT:x1 |
| 19.5 | 50%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x9 | N/A | boi_RT:x1 |
| 19.6 | 50%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x9 | N/A | boi_RT:x1 |
| 19.7 | 50%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x9 | N/A | boi_RT:x1 |
| 19.8 | 50%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x9 | N/A | boi_RT:x1 |
| 19.9 | 50%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x9 | N/A | boi_RT:x1 |
| 20.1 | 100%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 20.2 | 100%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 20.3 | 100%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 20.4 | 100%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 20.5 | 100%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 20.6 | 100%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 20.7 | 100%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 20.8 | 100%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 20.9 | 100%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 21.1 | 350%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x55 | N/A | boi_RT:x1 |
| 21.2 | 350%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x55 | N/A | boi_RT:x1 |
| 21.3 | 350%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x55 | N/A | boi_RT:x1 |
| 21.4 | 350%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x55 | N/A | boi_RT:x1 |
| 21.5 | 350%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x55 | N/A | boi_RT:x1 |
| 21.6 | 350%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x55 | N/A | boi_RT:x1 |
| 21.7 | 350%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x55 | N/A | boi_RT:x1 |
| 21.8 | 350%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x55 | N/A | boi_RT:x1 |
| 21.9 | 350%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x55 | N/A | boi_RT:x1 |
| 22.1 | 1250%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 22.2 | 1250%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 22.3 | 1250%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 22.4 | 1250%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 22.5 | 1250%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 22.6 | 1250%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 22.7 | 1250%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 22.8 | 1250%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 22.9 | 1250%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 23.1 | Risk weighted assets calculated by bank/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 23.2 | Risk weighted assets calculated by bank/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 23.3 | Risk weighted assets calculated by bank/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 23.4 | Risk weighted assets calculated by bank/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 23.5 | Risk weighted assets calculated by bank/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 23.6 | Risk weighted assets calculated by bank/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 23.7 | Risk weighted assets calculated by bank/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 23.8 | Risk weighted assets calculated by bank/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 23.9 | Risk weighted assets calculated by bank/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x28 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| r31.1 | Re-securitization exposures/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r31.2 | Re-securitization exposures/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r31.3 | Re-securitization exposures/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r31.4 | Re-securitization exposures/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r31.5 | Re-securitization exposures/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r31.6 | Re-securitization exposures/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r31.7 | Re-securitization exposures/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r31.8 | Re-securitization exposures/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| r31.9 | Re-securitization exposures/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | N/A | N/A | boi_RT:x1 |
| 24.1 | 40%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x52 | N/A | boi_RT:x1 |
| 24.2 | 40%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x52 | N/A | boi_RT:x1 |
| 24.3 | 40%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x52 | N/A | boi_RT:x1 |
| 24.4 | 40%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x52 | N/A | boi_RT:x1 |
| 24.5 | 40%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x52 | N/A | boi_RT:x1 |
| 24.6 | 40%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x52 | N/A | boi_RT:x1 |
| 24.7 | 40%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x52 | N/A | boi_RT:x1 |
| 24.8 | 40%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x52 | N/A | boi_RT:x1 |
| 24.9 | 40%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x52 | N/A | boi_RT:x1 |
| 25.1 | 100%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 25.2 | 100%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 25.3 | 100%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 25.4 | 100%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 25.5 | 100%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 25.6 | 100%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 25.7 | 100%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 25.8 | 100%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 25.9 | 100%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x11 | N/A | boi_RT:x1 |
| 26.1 | 225%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x53 | N/A | boi_RT:x1 |
| 26.2 | 225%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x53 | N/A | boi_RT:x1 |
| 26.3 | 225%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x53 | N/A | boi_RT:x1 |
| 26.4 | 225%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x53 | N/A | boi_RT:x1 |
| 26.5 | 225%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x53 | N/A | boi_RT:x1 |
| 26.6 | 225%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x53 | N/A | boi_RT:x1 |
| 26.7 | 225%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x53 | N/A | boi_RT:x1 |
| 26.8 | 225%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x53 | N/A | boi_RT:x1 |
| 26.9 | 225%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x53 | N/A | boi_RT:x1 |
| 27.1 | 650%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x56 | N/A | boi_RT:x1 |
| 27.2 | 650%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x56 | N/A | boi_RT:x1 |
| 27.3 | 650%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x56 | N/A | boi_RT:x1 |
| 27.4 | 650%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x56 | N/A | boi_RT:x1 |
| 27.5 | 650%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x56 | N/A | boi_RT:x1 |
| 27.6 | 650%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x56 | N/A | boi_RT:x1 |
| 27.7 | 650%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x56 | N/A | boi_RT:x1 |
| 27.8 | 650%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x56 | N/A | boi_RT:x1 |
| 27.9 | 650%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x56 | N/A | boi_RT:x1 |
| 28.1 | 1250%/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 28.2 | 1250%/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 28.3 | 1250%/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 28.4 | 1250%/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 28.5 | 1250%/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 28.6 | 1250%/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 28.7 | 1250%/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 28.8 | 1250%/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 28.9 | 1250%/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x57 | N/A | boi_RT:x1 |
| 29.1 | Risk weighted assets calculated by bank/Total securitization exposures before credit loss provision | boi_met:mi17 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 29.2 | Risk weighted assets calculated by bank/Total securitization exposures after credit loss provision | boi_met:mi18 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 29.3 | Risk weighted assets calculated by bank/Synthetic securitization Protection of credit against securitization exposures (-) | boi_met:mi529 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 29.4 | Risk weighted assets calculated by bank/Sums subtracted (-) | boi_met:mi22 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 29.5 | Risk weighted assets calculated by bank/Sums added (+) | boi_met:mi23 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 29.6 | Risk weighted assets calculated by bank/Sum subtracted incl. exposure volatility adjustment (-) | boi_met:mi530 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 29.7 | Risk weighted assets calculated by bank/Exposure size after credit risk mitigation (before conversion into credit) | boi_met:mi28 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 29.8 | Risk weighted assets calculated by bank/Exposure size after conversion into credit | boi_met:mi29 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |
| 29.9 | Risk weighted assets calculated by bank/Risk-weighted assets (RWA) | boi_met:mi30 | xbrli:monetaryItemType | instant | boi_BC:x16 | boi_CS:x2 | boi_EC:x27 | boi_MC:x250 | boi_PI:x45 | N/A | boi_RT:x1 |