| r0.1 | label_boi_a2/Included companies | | | | N/A | N/A | boi_IP:x23 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r0.2 | label_boi_a2/consolidated companies | | | | N/A | N/A | boi_IP:x26 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r0.3 | label_boi_a2/Total | | | | N/A | N/A | boi_IP:x31 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r1.1 | Consolidated/Included companies | | | | N/A | boi_CS:x2 | boi_IP:x23 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r1.2 | Consolidated/consolidated companies | | | | N/A | boi_CS:x2 | boi_IP:x26 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r1.3 | Consolidated/Total | | | | N/A | boi_CS:x2 | boi_IP:x31 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 1.1 | Investment in shares using balance-sheet value method (including goodwill)/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | N/A |
| 1.2 | Investment in shares using balance-sheet value method (including goodwill)/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | N/A |
| 1.3 | Investment in shares using balance-sheet value method (including goodwill)/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | N/A |
| r3.1 | Other investments/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r3.2 | Other investments/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r3.3 | Other investments/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 2.1 | payments on account of shares/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x684 | N/A | N/A | boi_RP:x24 | N/A |
| 2.2 | payments on account of shares/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x684 | N/A | N/A | boi_RP:x24 | N/A |
| 2.3 | payments on account of shares/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x684 | N/A | N/A | boi_RP:x24 | N/A |
| 3.1 | Certificates of rights to purchase shares/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x685 | N/A | N/A | boi_RP:x24 | N/A |
| 3.2 | Certificates of rights to purchase shares/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x685 | N/A | N/A | boi_RP:x24 | N/A |
| 3.3 | Certificates of rights to purchase shares/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x685 | N/A | N/A | boi_RP:x24 | N/A |
| 4.1 | Other benefits/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x686 | N/A | N/A | boi_RP:x24 | N/A |
| 4.2 | Other benefits/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x686 | N/A | N/A | boi_RP:x24 | N/A |
| 4.3 | Other benefits/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x686 | N/A | N/A | boi_RP:x24 | N/A |
| 5.1 | Convertible securities/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x687 | N/A | N/A | boi_RP:x24 | N/A |
| 5.2 | Convertible securities/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x687 | N/A | N/A | boi_RP:x24 | N/A |
| 5.3 | Convertible securities/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x687 | N/A | N/A | boi_RP:x24 | N/A |
| 6.1 | Subordinated capital notes/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x688 | N/A | N/A | boi_RP:x24 | N/A |
| 6.2 | Subordinated capital notes/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x688 | N/A | N/A | boi_RP:x24 | N/A |
| 6.3 | Subordinated capital notes/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x688 | N/A | N/A | boi_RP:x24 | N/A |
| 7.1 | Owners loans/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x689 | N/A | N/A | boi_RP:x24 | N/A |
| 7.2 | Owners loans/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x689 | N/A | N/A | boi_RP:x24 | N/A |
| 7.3 | Owners loans/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x689 | N/A | N/A | boi_RP:x24 | N/A |
| 8.1 | Total investments/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x54 | N/A | N/A | boi_RP:x24 | N/A |
| 8.2 | Total investments/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x54 | N/A | N/A | boi_RP:x24 | N/A |
| 8.3 | Total investments/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x54 | N/A | N/A | boi_RP:x24 | N/A |
| 9.1 | Thereof: profit (loss) from date of purchase/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x23 | boi_MC:x191 | N/A | N/A | boi_RP:x24 | N/A |
| 9.2 | Thereof: profit (loss) from date of purchase/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x26 | boi_MC:x191 | N/A | N/A | boi_RP:x24 | N/A |
| 9.3 | Thereof: profit (loss) from date of purchase/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x31 | boi_MC:x191 | N/A | N/A | boi_RP:x24 | N/A |
| r12.1 | From equity:/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x23 | boi_MC:x399 | N/A | N/A | boi_RP:x24 | N/A |
| r12.2 | From equity:/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x26 | boi_MC:x399 | N/A | N/A | boi_RP:x24 | N/A |
| r12.3 | From equity:/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x31 | boi_MC:x399 | N/A | N/A | boi_RP:x24 | N/A |
| 10.1 | adjustments from presentation of securities available for sale/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x23 | boi_MC:x399 | N/A | boi_PL:x1 | boi_RP:x24 | N/A |
| 10.2 | adjustments from presentation of securities available for sale/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x26 | boi_MC:x399 | N/A | boi_PL:x1 | boi_RP:x24 | N/A |
| 10.3 | adjustments from presentation of securities available for sale/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x31 | boi_MC:x399 | N/A | boi_PL:x1 | boi_RP:x24 | N/A |
| 11.1 | Adjustments from translation of financial statements/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x23 | boi_MC:x399 | N/A | boi_PL:x30 | boi_RP:x24 | N/A |
| 11.2 | Adjustments from translation of financial statements/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x26 | boi_MC:x399 | N/A | boi_PL:x30 | boi_RP:x24 | N/A |
| 11.3 | Adjustments from translation of financial statements/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x31 | boi_MC:x399 | N/A | boi_PL:x30 | boi_RP:x24 | N/A |
| 12.1 | Other/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x23 | boi_MC:x399 | N/A | boi_PL:x27 | boi_RP:x24 | N/A |
| 12.2 | Other/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x26 | boi_MC:x399 | N/A | boi_PL:x27 | boi_RP:x24 | N/A |
| 12.3 | Other/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x2 | boi_IP:x31 | boi_MC:x399 | N/A | boi_PL:x27 | boi_RP:x24 | N/A |
| r16.1 | goodwill/Included companies | | | | N/A | boi_CS:x2 | boi_IP:x23 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r16.2 | goodwill/consolidated companies | | | | N/A | boi_CS:x2 | boi_IP:x26 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r16.3 | goodwill/Total | | | | N/A | boi_CS:x2 | boi_IP:x31 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 13.1 | Original sum/Included companies | boi_met:mi376 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x837 | N/A | N/A | boi_RP:x24 | N/A |
| 13.2 | Original sum/consolidated companies | boi_met:mi376 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x837 | N/A | N/A | boi_RP:x24 | N/A |
| 13.3 | Original sum/Total | boi_met:mi376 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x837 | N/A | N/A | boi_RP:x24 | N/A |
| r18.1 | Details about trade all investments:/Included companies | | | | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| r18.2 | Details about trade all investments:/consolidated companies | | | | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| r18.3 | Details about trade all investments:/Total | | | | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 15.1 | book value/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 15.2 | book value/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 15.3 | book value/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 16.1 | Market value/Included companies | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x23 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 16.2 | Market value/consolidated companies | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x26 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 16.3 | Market value/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_IP:x31 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 17.1 | Bank's share in included companies profit, pre-tax/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_IP:x23 | boi_MC:x690 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 17.2 | Bank's share in included companies profit, pre-tax/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_IP:x26 | boi_MC:x690 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 17.3 | Bank's share in included companies profit, pre-tax/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_IP:x31 | boi_MC:x690 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 18.1 | Losses from decrease in value of included companies/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_IP:x23 | boi_MC:x691 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 18.2 | Losses from decrease in value of included companies/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_IP:x26 | boi_MC:x691 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 18.3 | Losses from decrease in value of included companies/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x2 | boi_IP:x31 | boi_MC:x691 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 19.1 | Translation of losses from decrease in value of included companies/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | boi_IP:x23 | boi_MC:x692 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 19.2 | Translation of losses from decrease in value of included companies/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | boi_IP:x26 | boi_MC:x692 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 19.3 | Translation of losses from decrease in value of included companies/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | boi_IP:x31 | boi_MC:x692 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| r24.1 | Tax provision:/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x23 | N/A | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| r24.2 | Tax provision:/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x26 | N/A | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| r24.3 | Tax provision:/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x31 | N/A | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 20.1 | current/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x23 | boi_MC:x694 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 20.2 | current/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x26 | boi_MC:x694 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 20.3 | current/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x31 | boi_MC:x694 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 21.1 | Deferred/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x23 | boi_MC:x695 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 21.2 | Deferred/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x26 | boi_MC:x695 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 21.3 | Deferred/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x31 | boi_MC:x695 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 22.1 | Total tax provision/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x23 | boi_MC:x693 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 22.2 | Total tax provision/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x26 | boi_MC:x693 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 22.3 | Total tax provision/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x2 | boi_IP:x31 | boi_MC:x693 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 23.1 | Share in included companies profit, after tax/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_IP:x23 | boi_MC:x191 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 23.2 | Share in included companies profit, after tax/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_IP:x26 | boi_MC:x191 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 23.3 | Share in included companies profit, after tax/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x2 | boi_IP:x31 | boi_MC:x191 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| r29.1 | Company/Included companies | | | | N/A | boi_CS:x1 | boi_IP:x23 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r29.2 | Company/consolidated companies | | | | N/A | boi_CS:x1 | boi_IP:x26 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r29.3 | Company/Total | | | | N/A | boi_CS:x1 | boi_IP:x31 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 24.1 | Investment in shares using balance-sheet value method (including goodwill)/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | N/A |
| 24.2 | Investment in shares using balance-sheet value method (including goodwill)/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | N/A |
| 24.3 | Investment in shares using balance-sheet value method (including goodwill)/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | N/A |
| r31.1 | Other investments/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r31.2 | Other investments/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r31.3 | Other investments/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 25.1 | payments on account of shares/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x684 | N/A | N/A | boi_RP:x24 | N/A |
| 25.2 | payments on account of shares/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x684 | N/A | N/A | boi_RP:x24 | N/A |
| 25.3 | payments on account of shares/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x684 | N/A | N/A | boi_RP:x24 | N/A |
| 26.1 | Certificates of rights to purchase shares/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x685 | N/A | N/A | boi_RP:x24 | N/A |
| 26.2 | Certificates of rights to purchase shares/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x685 | N/A | N/A | boi_RP:x24 | N/A |
| 26.3 | Certificates of rights to purchase shares/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x685 | N/A | N/A | boi_RP:x24 | N/A |
| 27.1 | Other benefits/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x686 | N/A | N/A | boi_RP:x24 | N/A |
| 27.2 | Other benefits/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x686 | N/A | N/A | boi_RP:x24 | N/A |
| 27.3 | Other benefits/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x686 | N/A | N/A | boi_RP:x24 | N/A |
| 28.1 | Convertible securities/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x687 | N/A | N/A | boi_RP:x24 | N/A |
| 28.2 | Convertible securities/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x687 | N/A | N/A | boi_RP:x24 | N/A |
| 28.3 | Convertible securities/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x687 | N/A | N/A | boi_RP:x24 | N/A |
| 29.1 | Subordinated capital notes/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x688 | N/A | N/A | boi_RP:x24 | N/A |
| 29.2 | Subordinated capital notes/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x688 | N/A | N/A | boi_RP:x24 | N/A |
| 29.3 | Subordinated capital notes/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x688 | N/A | N/A | boi_RP:x24 | N/A |
| 30.1 | Owners loans/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x689 | N/A | N/A | boi_RP:x24 | N/A |
| 30.2 | Owners loans/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x689 | N/A | N/A | boi_RP:x24 | N/A |
| 30.3 | Owners loans/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x689 | N/A | N/A | boi_RP:x24 | N/A |
| 31.1 | Total investments/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x54 | N/A | N/A | boi_RP:x24 | N/A |
| 31.2 | Total investments/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x54 | N/A | N/A | boi_RP:x24 | N/A |
| 31.3 | Total investments/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x54 | N/A | N/A | boi_RP:x24 | N/A |
| 32.1 | Thereof: profit (loss) from date of purchase/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x23 | boi_MC:x191 | N/A | N/A | boi_RP:x24 | N/A |
| 32.2 | Thereof: profit (loss) from date of purchase/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x26 | boi_MC:x191 | N/A | N/A | boi_RP:x24 | N/A |
| 32.3 | Thereof: profit (loss) from date of purchase/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x31 | boi_MC:x191 | N/A | N/A | boi_RP:x24 | N/A |
| r40.1 | From equity:/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x23 | boi_MC:x399 | N/A | N/A | boi_RP:x24 | N/A |
| r40.2 | From equity:/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x26 | boi_MC:x399 | N/A | N/A | boi_RP:x24 | N/A |
| r40.3 | From equity:/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x31 | boi_MC:x399 | N/A | N/A | boi_RP:x24 | N/A |
| 33.1 | adjustments from presentation of securities available for sale/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x23 | boi_MC:x399 | N/A | boi_PL:x1 | boi_RP:x24 | N/A |
| 33.2 | adjustments from presentation of securities available for sale/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x26 | boi_MC:x399 | N/A | boi_PL:x1 | boi_RP:x24 | N/A |
| 33.3 | adjustments from presentation of securities available for sale/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x31 | boi_MC:x399 | N/A | boi_PL:x1 | boi_RP:x24 | N/A |
| 34.1 | Adjustments from translation of financial statements/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x23 | boi_MC:x399 | N/A | boi_PL:x30 | boi_RP:x24 | N/A |
| 34.2 | Adjustments from translation of financial statements/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x26 | boi_MC:x399 | N/A | boi_PL:x30 | boi_RP:x24 | N/A |
| 34.3 | Adjustments from translation of financial statements/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x31 | boi_MC:x399 | N/A | boi_PL:x30 | boi_RP:x24 | N/A |
| 35.1 | Other/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x23 | boi_MC:x399 | N/A | boi_PL:x27 | boi_RP:x24 | N/A |
| 35.2 | Other/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x26 | boi_MC:x399 | N/A | boi_PL:x27 | boi_RP:x24 | N/A |
| 35.3 | Other/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x3 | boi_CS:x1 | boi_IP:x31 | boi_MC:x399 | N/A | boi_PL:x27 | boi_RP:x24 | N/A |
| r44.1 | goodwill/Included companies | | | | N/A | boi_CS:x1 | boi_IP:x23 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r44.2 | goodwill/consolidated companies | | | | N/A | boi_CS:x1 | boi_IP:x26 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| r44.3 | goodwill/Total | | | | N/A | boi_CS:x1 | boi_IP:x31 | N/A | N/A | N/A | boi_RP:x24 | N/A |
| 36.1 | Original sum/Included companies | boi_met:mi376 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x837 | N/A | N/A | boi_RP:x24 | N/A |
| 36.2 | Original sum/consolidated companies | boi_met:mi376 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x837 | N/A | N/A | boi_RP:x24 | N/A |
| 36.3 | Original sum/Total | boi_met:mi376 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x837 | N/A | N/A | boi_RP:x24 | N/A |
| r46.1 | Details about trade all investments:/Included companies | | | | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| r46.2 | Details about trade all investments:/consolidated companies | | | | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| r46.3 | Details about trade all investments:/Total | | | | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 38.1 | book value/Included companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 38.2 | book value/consolidated companies | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 38.3 | book value/Total | boi_met:mi1 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 39.1 | Market value/Included companies | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x23 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 39.2 | Market value/consolidated companies | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x26 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 39.3 | Market value/Total | boi_met:mi5 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x1 | boi_IP:x31 | boi_MC:x683 | N/A | N/A | boi_RP:x24 | boi_SE:x91 |
| 40.1 | Bank's share in included companies' profit, pre-tax/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_IP:x23 | boi_MC:x690 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 40.2 | Bank's share in included companies' profit, pre-tax/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_IP:x26 | boi_MC:x690 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 40.3 | Bank's share in included companies' profit, pre-tax/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_IP:x31 | boi_MC:x690 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 41.1 | Losses from decrease in value of included companies/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | boi_IP:x23 | boi_MC:x691 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 41.2 | Losses from decrease in value of included companies/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | boi_IP:x26 | boi_MC:x691 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 41.3 | Losses from decrease in value of included companies/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x10 | boi_CS:x1 | boi_IP:x31 | boi_MC:x691 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 42.1 | Translation of losses from decrease in value of included companies/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x1 | boi_IP:x23 | boi_MC:x692 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 42.2 | Translation of losses from decrease in value of included companies/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x1 | boi_IP:x26 | boi_MC:x692 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 42.3 | Translation of losses from decrease in value of included companies/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x1 | boi_IP:x31 | boi_MC:x692 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| r52.1 | Tax provision:/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x23 | N/A | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| r52.2 | Tax provision:/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x26 | N/A | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| r52.3 | Tax provision:/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x31 | N/A | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 43.1 | current/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x23 | boi_MC:x694 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 43.2 | current/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x26 | boi_MC:x694 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 43.3 | current/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x31 | boi_MC:x694 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 44.1 | Deferred/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x23 | boi_MC:x695 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 44.2 | Deferred/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x26 | boi_MC:x695 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 44.3 | Deferred/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x31 | boi_MC:x695 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 45.1 | Total tax provision/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x23 | boi_MC:x693 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 45.2 | Total tax provision/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x26 | boi_MC:x693 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 45.3 | Total tax provision/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x12 | boi_CS:x1 | boi_IP:x31 | boi_MC:x693 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 46.1 | Share in included companies' profit, after tax/Included companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_IP:x23 | boi_MC:x191 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 46.2 | Share in included companies' profit, after tax/consolidated companies | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_IP:x26 | boi_MC:x191 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |
| 46.3 | Share in included companies' profit, after tax/Total | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x11 | boi_CS:x1 | boi_IP:x31 | boi_MC:x191 | boi_MU:x1 | N/A | boi_RP:x24 | N/A |