| r0.2 | label_boi_a2/Present off-balance-sheet credit risk | boi_met:mi187 | xbrli:monetaryItemType | instant | boi_BC:x6 | boi_CS:x2 | boi_GA:x2 | boi_MC:x879 | boi_RP:x24 | boi_SE:x9 | N/A | N/A |
| 1.2 | External credit rating: AAA to AA-/Present off-balance-sheet credit risk | boi_met:mi187 | xbrli:monetaryItemType | instant | boi_BC:x6 | boi_CS:x2 | boi_GA:x2 | boi_MC:x879 | boi_RP:x24 | boi_SE:x9 | boi_ST:x91 | N/A |
| 2.2 | A+ to A-/Present off-balance-sheet credit risk | boi_met:mi187 | xbrli:monetaryItemType | instant | boi_BC:x6 | boi_CS:x2 | boi_GA:x2 | boi_MC:x879 | boi_RP:x24 | boi_SE:x9 | boi_ST:x92 | N/A |
| 3.2 | BBB+ to BBB-/Present off-balance-sheet credit risk | boi_met:mi187 | xbrli:monetaryItemType | instant | boi_BC:x6 | boi_CS:x2 | boi_GA:x2 | boi_MC:x879 | boi_RP:x24 | boi_SE:x9 | boi_ST:x93 | N/A |
| 4.2 | BB+ to B-/Present off-balance-sheet credit risk | boi_met:mi187 | xbrli:monetaryItemType | instant | boi_BC:x6 | boi_CS:x2 | boi_GA:x2 | boi_MC:x879 | boi_RP:x24 | boi_SE:x9 | boi_ST:x94 | N/A |
| 5.2 | Less than: B-/Present off-balance-sheet credit risk | boi_met:mi187 | xbrli:monetaryItemType | instant | boi_BC:x6 | boi_CS:x2 | boi_GA:x2 | boi_MC:x879 | boi_RP:x24 | boi_SE:x9 | boi_ST:x95 | N/A |
| 6.2 | Unrated/Present off-balance-sheet credit risk | boi_met:mi187 | xbrli:monetaryItemType | instant | boi_BC:x6 | boi_CS:x2 | boi_GA:x2 | boi_MC:x879 | boi_RP:x24 | boi_SE:x9 | boi_ST:x17 | N/A |
| 7.2 | Total present credit exposure to foreign financial institutions/Present off-balance-sheet credit risk | boi_met:mi187 | xbrli:monetaryItemType | instant | boi_BC:x6 | boi_CS:x2 | boi_GA:x2 | boi_MC:x879 | boi_RP:x24 | boi_SE:x9 | N/A | N/A |
| 8.2 | Of which: Problematic commercial credit risk/Present off-balance-sheet credit risk | boi_met:mi187 | xbrli:monetaryItemType | instant | boi_BC:x6 | boi_CS:x2 | boi_GA:x2 | boi_MC:x879 | boi_RP:x24 | boi_SE:x9 | N/A | boi_ST:x2 |