| r0.1 | label_boi_a2/Balance of debts for which individual provision exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x6 | boi_ST:x212 |
| r0.2 | label_boi_a2/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x6 | boi_ST:x212 |
| r0.3 | label_boi_a2/Contractual balance of impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x8 | boi_ST:x212 |
| r0.4 | label_boi_a2/Total balance of impaired debts | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | boi_MU:x1 | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x212 |
| r0.5 | label_boi_a2/Contractual balance of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x212 |
| r0.6 | label_boi_a2/Interest income posted | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | boi_MC:x125 | boi_MC:x8 | boi_MU:x1 | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x212 |
| 12.1 | If the debts that do not accrue had accrued interest under the original conditions, interest income would have been recorded in total/Balance of debts for which individual provision exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x6 | boi_ST:x212 |
| 12.2 | If the debts that do not accrue had accrued interest under the original conditions, interest income would have been recorded in total/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x6 | boi_ST:x212 |
| 12.3 | If the debts that do not accrue had accrued interest under the original conditions, interest income would have been recorded in total/Contractual balance of impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x8 | boi_ST:x212 |
| 12.4 | If the debts that do not accrue had accrued interest under the original conditions, interest income would have been recorded in total/Total balance of impaired debts | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | boi_MU:x1 | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x212 |
| 12.5 | If the debts that do not accrue had accrued interest under the original conditions, interest income would have been recorded in total/Contractual balance of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x212 |
| 12.6 | If the debts that do not accrue had accrued interest under the original conditions, interest income would have been recorded in total/Interest income posted | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | boi_MC:x125 | boi_MC:x8 | boi_MU:x1 | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x212 |
| 13.1 | Total debt balance The average record of debts not accumulating/Balance of debts for which individual provision exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x6 | boi_ST:x212 |
| 13.2 | Total debt balance The average record of debts not accumulating/Balance of individual allowance | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x6 | boi_ST:x212 |
| 13.3 | Total debt balance The average record of debts not accumulating/Contractual balance of impaired debts for which no individual allowance exists | boi_met:mi2 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | boi_ST:x8 | boi_ST:x212 |
| 13.4 | Total debt balance The average record of debts not accumulating/Total balance of impaired debts | boi_met:md86 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | boi_MU:x1 | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x212 |
| 13.5 | Total debt balance The average record of debts not accumulating/Contractual balance of impaired debts | boi_met:mi9 | xbrli:monetaryItemType | instant | boi_BC:x1 | boi_CS:x2 | boi_MC:x8 | N/A | N/A | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x212 |
| 13.6 | Total debt balance The average record of debts not accumulating/Interest income posted | boi_met:md13 | xbrli:monetaryItemType | instant | boi_BC:x9 | boi_CS:x2 | boi_MC:x125 | boi_MC:x8 | boi_MU:x1 | boi_RP:x24 | boi_SE:x16 | N/A | boi_ST:x212 |