| r0.1 | label_boi_a2/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | N/A | N/A | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| r0.2 | label_boi_a2/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | N/A | N/A | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| r0.3 | label_boi_a2/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | N/A | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r0.4 | label_boi_a2/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | N/A | N/A | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| r0.5 | label_boi_a2/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | N/A | N/A | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| r0.6 | label_boi_a2/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | N/A | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 1.1 | Interest rate contracts/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | boi_RT:x8 |
| 1.2 | Interest rate contracts/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | boi_RT:x8 |
| 1.3 | Interest rate contracts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | boi_RT:x8 |
| 1.4 | Interest rate contracts/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | boi_RT:x8 |
| 1.5 | Interest rate contracts/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | boi_RT:x8 |
| 1.6 | Interest rate contracts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | boi_RT:x8 |
| 2.1 | Of which: hedging derivatives/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | boi_PL:x11 | boi_RP:x24 | boi_RT:x8 |
| 2.2 | Of which: hedging derivatives/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | boi_PL:x11 | boi_RP:x24 | boi_RT:x8 |
| 2.3 | Of which: hedging derivatives/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | boi_PL:x11 | boi_RP:x24 | boi_RT:x8 |
| 2.4 | Of which: hedging derivatives/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | boi_PL:x11 | boi_RP:x24 | boi_RT:x8 |
| 2.5 | Of which: hedging derivatives/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | boi_PL:x11 | boi_RP:x24 | boi_RT:x8 |
| 2.6 | Of which: hedging derivatives/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | boi_PL:x11 | boi_RP:x24 | boi_RT:x8 |
| 3.1 | Foreign currency contracts/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | boi_RT:x10 |
| 3.2 | Foreign currency contracts/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | boi_RT:x10 |
| 3.3 | Foreign currency contracts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | boi_RT:x10 |
| 3.4 | Foreign currency contracts/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | boi_RT:x10 |
| 3.5 | Foreign currency contracts/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | boi_RT:x10 |
| 3.6 | Foreign currency contracts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | boi_RT:x10 |
| 4.1 | Of which: hedging derivatives/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | boi_PL:x11 | boi_RP:x24 | boi_RT:x10 |
| 4.2 | Of which: hedging derivatives/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | boi_PL:x11 | boi_RP:x24 | boi_RT:x10 |
| 4.3 | Of which: hedging derivatives/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | boi_PL:x11 | boi_RP:x24 | boi_RT:x10 |
| 4.4 | Of which: hedging derivatives/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | boi_PL:x11 | boi_RP:x24 | boi_RT:x10 |
| 4.5 | Of which: hedging derivatives/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | boi_PL:x11 | boi_RP:x24 | boi_RT:x10 |
| 4.6 | Of which: hedging derivatives/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | boi_PL:x11 | boi_RP:x24 | boi_RT:x10 |
| 5.1 | Contracts in respect of shares/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | boi_RT:x9 |
| 5.2 | Contracts in respect of shares/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | boi_RT:x9 |
| 5.3 | Contracts in respect of shares/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | boi_RT:x9 |
| 5.4 | Contracts in respect of shares/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | boi_RT:x9 |
| 5.5 | Contracts in respect of shares/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | boi_RT:x9 |
| 5.6 | Contracts in respect of shares/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | boi_RT:x9 |
| 6.1 | Commodity and other contracts/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | boi_RT:x16 |
| 6.2 | Commodity and other contracts/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | boi_RT:x16 |
| 6.3 | Commodity and other contracts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | boi_RT:x16 |
| 6.4 | Commodity and other contracts/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | boi_RT:x16 |
| 6.5 | Commodity and other contracts/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | boi_RT:x16 |
| 6.6 | Commodity and other contracts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x946 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | boi_RT:x16 |
| 7.1 | Credit contracts/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x945 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 7.2 | Credit contracts/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x945 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 7.3 | Credit contracts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x945 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | N/A |
| 7.4 | Credit contracts/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x945 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 7.5 | Credit contracts/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x945 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 7.6 | Credit contracts/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x945 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | N/A |
| 8.1 | Total assets/liabilities in respect of derivatives, gross/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 8.2 | Total assets/liabilities in respect of derivatives, gross/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 8.3 | Total assets/liabilities in respect of derivatives, gross/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | N/A |
| 8.4 | Total assets/liabilities in respect of derivatives, gross/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 8.5 | Total assets/liabilities in respect of derivatives, gross/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 8.6 | Total assets/liabilities in respect of derivatives, gross/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | N/A |
| 9.1 | Of which: Embedded/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x959 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 9.2 | Of which: Embedded/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x959 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 9.3 | Of which: Embedded/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x959 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | N/A |
| 9.4 | Of which: Embedded/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x959 | boi_NE:x1 | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 9.5 | Of which: Embedded/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x959 | boi_NE:x1 | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 9.6 | Of which: Embedded/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x959 | boi_NE:x1 | N/A | N/A | boi_RP:x24 | N/A |
| 10.1 | Sum of fair value which were compensated in the balance sheet/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | boi_NE:x2 | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 10.2 | Sum of fair value which were compensated in the balance sheet/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | boi_NE:x2 | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 10.3 | Sum of fair value which were compensated in the balance sheet/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | boi_NE:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 10.4 | Sum of fair value which were compensated in the balance sheet/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | boi_NE:x2 | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 10.5 | Sum of fair value which were compensated in the balance sheet/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | boi_NE:x2 | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 10.6 | Sum of fair value which were compensated in the balance sheet/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | boi_NE:x2 | N/A | N/A | boi_RP:x24 | N/A |
| 11.1 | Balance of assets due to derivative istruments/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | N/A | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 11.2 | Balance of assets due to derivative istruments/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | N/A | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 11.3 | Balance of assets due to derivative istruments/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 11.4 | Balance of assets due to derivative istruments/Trading derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | N/A | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 11.5 | Balance of assets due to derivative istruments/Non trade derivatives | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | N/A | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 11.6 | Balance of assets due to derivative istruments/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 12.1 | of which: not under net account agreements or similar agreements/Trading derivatives | boi_met:mi205 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | N/A | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 12.2 | of which: not under net account agreements or similar agreements/Non trade derivatives | boi_met:mi205 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | N/A | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 12.3 | of which: not under net account agreements or similar agreements/Total | boi_met:mi205 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x944 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 12.4 | of which: not under net account agreements or similar agreements/Trading derivatives | boi_met:mi205 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | N/A | boi_PL:x2 | N/A | boi_RP:x24 | N/A |
| 12.5 | of which: not under net account agreements or similar agreements/Non trade derivatives | boi_met:mi205 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | N/A | boi_PL:x15 | N/A | boi_RP:x24 | N/A |
| 12.6 | of which: not under net account agreements or similar agreements/Total | boi_met:mi205 | xbrli:monetaryItemType | instant | boi_BC:x2 | boi_CS:x2 | boi_MC:x944 | N/A | N/A | N/A | boi_RP:x24 | N/A |