| r0.1 | label_boi_a2/Avg. gross balance | | | | N/A | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | N/A | N/A | boi_MU:x1 | N/A | N/A |
| r0.4 | label_boi_a2/Avg. gross balance | | | | N/A | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | N/A | N/A | boi_MU:x1 | N/A | N/A |
| r0.7 | label_boi_a2/Avg. gross balance | | | | N/A | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | N/A | N/A | boi_MU:x1 | N/A | N/A |
| r1.1 | Assets/Avg. gross balance | | | | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | N/A | N/A | boi_MU:x1 | N/A | N/A |
| r1.4 | Assets/Avg. gross balance | | | | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | N/A | N/A | boi_MU:x1 | N/A | N/A |
| r1.7 | Assets/Avg. gross balance | | | | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | N/A | N/A | boi_MU:x1 | N/A | N/A |
| r2.1 | Interest-bearing assets/Avg. gross balance | | | | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | N/A | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| r2.4 | Interest-bearing assets/Avg. gross balance | | | | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | N/A | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| r2.7 | Interest-bearing assets/Avg. gross balance | | | | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | N/A | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 1.1 | Credit to the public/Avg. gross balance | boi_met:md87 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x16 |
| 1.4 | Credit to the public/Avg. gross balance | boi_met:md87 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x16 |
| 1.7 | Credit to the public/Avg. gross balance | boi_met:md87 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x16 |
| 2.1 | Thereof: housing credit, fixed rate/Avg. gross balance | boi_met:md87 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_CU:x23 | boi_CU:x6 | boi_GA:x1 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x15 |
| 2.4 | Thereof: housing credit, fixed rate/Avg. gross balance | boi_met:md87 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_CU:x23 | boi_CU:x6 | boi_GA:x2 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x15 |
| 2.7 | Thereof: housing credit, fixed rate/Avg. gross balance | boi_met:md87 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_CU:x23 | boi_CU:x6 | N/A | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x15 |
| 3.1 | Thereof: housing credit, floating rate/Avg. gross balance | boi_met:md87 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_CU:x24 | boi_CU:x6 | boi_GA:x1 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x15 |
| 3.4 | Thereof: housing credit, floating rate/Avg. gross balance | boi_met:md87 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_CU:x24 | boi_CU:x6 | boi_GA:x2 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x15 |
| 3.7 | Thereof: housing credit, floating rate/Avg. gross balance | boi_met:md87 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CL:x35 | boi_CS:x2 | boi_CU:x24 | boi_CU:x6 | N/A | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x15 |
| 4.1 | Credit to government/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x11 |
| 4.4 | Credit to government/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x11 |
| 4.7 | Credit to government/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x11 |
| 5.1 | Deposits with banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x5 |
| 5.4 | Deposits with banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x5 |
| 5.7 | Deposits with banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x8 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x5 |
| 6.1 | Deposits with central banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x9 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x2 |
| 6.4 | Deposits with central banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x9 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x2 |
| 6.7 | Deposits with central banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x9 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x2 |
| 7.1 | Securities borrowed or acquired under repurchase agreements/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x28 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 7.4 | Securities borrowed or acquired under repurchase agreements/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x28 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 7.7 | Securities borrowed or acquired under repurchase agreements/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x28 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| r10.1 | Bonds/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| r10.4 | Bonds/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| r10.7 | Bonds/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 8.1 | Held to maturity/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | boi_PL:x5 | N/A |
| 8.4 | Held to maturity/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | boi_PL:x5 | N/A |
| 8.7 | Held to maturity/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | boi_PL:x5 | N/A |
| 9.1 | Available for sale/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | boi_PL:x1 | N/A |
| 9.4 | Available for sale/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | boi_PL:x1 | N/A |
| 9.7 | Available for sale/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | boi_PL:x1 | N/A |
| 10.1 | For trading/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | boi_PL:x2 | N/A |
| 10.4 | For trading/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | boi_PL:x2 | N/A |
| 10.7 | For trading/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | boi_PL:x2 | N/A |
| 11.1 | Total bonds/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 11.4 | Total bonds/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 11.7 | Total bonds/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 12.1 | Other assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x279 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 12.4 | Other assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x279 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 12.7 | Other assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x279 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 13.1 | Total interest-bearing assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x1 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 13.4 | Total interest-bearing assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x1 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 13.7 | Total interest-bearing assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x1 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 14.1 | Non-interest-bearing sums receivable on account of credit cards/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x143 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 14.4 | Non-interest-bearing sums receivable on account of credit cards/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x143 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 14.7 | Non-interest-bearing sums receivable on account of credit cards/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x143 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 15.1 | Other non-interest-bearing assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x280 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 15.4 | Other non-interest-bearing assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x280 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 15.7 | Other non-interest-bearing assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x280 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 16.1 | Total assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x1 | N/A | boi_MU:x1 | N/A | N/A |
| 16.4 | Total assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x1 | N/A | boi_MU:x1 | N/A | N/A |
| 16.7 | Total assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x1 | N/A | boi_MU:x1 | N/A | N/A |
| r20.1 | Liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | N/A | N/A | boi_MU:x1 | N/A | N/A |
| r20.4 | Liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | N/A | N/A | boi_MU:x1 | N/A | N/A |
| r20.7 | Liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | N/A | N/A | boi_MU:x1 | N/A | N/A |
| r21.1 | Interest-bearing liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | N/A | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| r21.4 | Interest-bearing liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | N/A | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| r21.7 | Interest-bearing liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | N/A | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 17.1 | Deposits from the public/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x16 |
| 17.4 | Deposits from the public/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x16 |
| 17.7 | Deposits from the public/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x16 |
| 18.1 | Deposits from government/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x11 |
| 18.4 | Deposits from government/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x11 |
| 18.7 | Deposits from government/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x11 |
| 19.1 | Deposits from central banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x2 |
| 19.4 | Deposits from central banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x2 |
| 19.7 | Deposits from central banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x2 |
| 20.1 | Deposits from banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x5 |
| 20.4 | Deposits from banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x5 |
| 20.7 | Deposits from banks/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x17 | boi_MC:x962 | boi_MU:x1 | N/A | boi_SE:x5 |
| 21.1 | Securities lent or sold under repurchase agreements/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x28 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 21.4 | Securities lent or sold under repurchase agreements/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x28 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 21.7 | Securities lent or sold under repurchase agreements/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x28 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 22.1 | Bonds/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 22.4 | Bonds/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 22.7 | Bonds/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x15 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 23.1 | Other liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x472 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 23.4 | Other liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x472 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 23.7 | Other liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x472 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 24.1 | Total interest-bearing liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x3 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 24.4 | Total interest-bearing liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x3 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 24.7 | Total interest-bearing liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x3 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 25.1 | Non-interest-bearing deposits from the public/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x276 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 25.4 | Non-interest-bearing deposits from the public/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x276 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 25.7 | Non-interest-bearing deposits from the public/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x276 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 26.1 | Non-interest-bearing sums payable on account of credit cards/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x143 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 26.4 | Non-interest-bearing sums payable on account of credit cards/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x143 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 26.7 | Non-interest-bearing sums payable on account of credit cards/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x143 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 27.1 | Other non-interest-bearing liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x277 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 27.4 | Other non-interest-bearing liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x277 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 27.7 | Other non-interest-bearing liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x277 | boi_MC:x914 | boi_MU:x1 | N/A | N/A |
| 28.1 | Total liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x3 | N/A | boi_MU:x1 | N/A | N/A |
| 28.4 | Total liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x3 | N/A | boi_MU:x1 | N/A | N/A |
| 28.7 | Total liabilities/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x2 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x3 | N/A | boi_MU:x1 | N/A | N/A |
| 30.1 | Net return on interest-bearing assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x1 | boi_MC:x1 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 30.4 | Net return on interest-bearing assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | boi_GA:x2 | boi_MC:x1 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |
| 30.7 | Net return on interest-bearing assets/Avg. gross balance | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | N/A | boi_CS:x2 | N/A | boi_CU:x6 | N/A | boi_MC:x1 | boi_MC:x962 | boi_MU:x1 | N/A | N/A |