| r0.1 | label_boi_a2/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | N/A | boi_RP:x24 |
| r0.2 | label_boi_a2/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | N/A | N/A | boi_RP:x24 |
| r1.1 | Cosolidated/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | N/A | boi_RP:x24 |
| r1.2 | Cosolidated/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | N/A | boi_RP:x24 |
| 1.1 | Documentary credit/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x70 | boi_RP:x24 |
| 1.2 | Documentary credit/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x70 | boi_RP:x24 |
| 2.1 | Credit guarantees/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x66 | boi_RP:x24 |
| 2.2 | Credit guarantees/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x66 | boi_RP:x24 |
| 3.1 | Of which: Guarantees for debt balances deriving from credit card transactions/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x506 | boi_RP:x24 |
| 3.2 | Of which: Guarantees for debt balances deriving from credit card transactions/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x506 | boi_RP:x24 |
| 4.1 | Guarantees to purchasers of homes/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x67 | boi_RP:x24 |
| 4.2 | Guarantees to purchasers of homes/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x67 | boi_RP:x24 |
| 5.1 | Other guarantees and liabilities/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x507 | boi_RP:x24 |
| 5.2 | Other guarantees and liabilities/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x507 | boi_RP:x24 |
| 6.1 | Unutilized credit facilities for card credits/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x74 | boi_RP:x24 |
| 6.2 | Unutilized credit facilities for card credits/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x74 | boi_RP:x24 |
| 7.1 | Unutilized revolving overdraft and other on-demand credit facilities/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x75 | boi_RP:x24 |
| 7.2 | Unutilized revolving overdraft and other on-demand credit facilities/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x75 | boi_RP:x24 |
| 8.1 | Irrevocable commitments to grant credit which has been approved but not yet drawn/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x77 | boi_RP:x24 |
| 8.2 | Irrevocable commitments to grant credit which has been approved but not yet drawn/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x77 | boi_RP:x24 |
| 9.1 | Commitments to issue guarantees/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x76 | boi_RP:x24 |
| 9.2 | Commitments to issue guarantees/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x76 | boi_RP:x24 |
| 10.1 | Total/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x65 | boi_RP:x24 |
| 10.2 | Total/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x2 | boi_MC:x65 | boi_RP:x24 |
| r12.1 | Bank/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | N/A | boi_RP:x24 |
| r12.2 | Bank/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | N/A | boi_RP:x24 |
| 11.1 | Documentary credit/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x70 | boi_RP:x24 |
| 11.2 | Documentary credit/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x70 | boi_RP:x24 |
| 12.1 | Credit guarantees/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x66 | boi_RP:x24 |
| 12.2 | Credit guarantees/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x66 | boi_RP:x24 |
| 13.1 | Of which: Guarantees for debt balances deriving from credit card transactions/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x506 | boi_RP:x24 |
| 13.2 | Of which: Guarantees for debt balances deriving from credit card transactions/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x506 | boi_RP:x24 |
| 14.1 | Guarantees to department purchases/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x67 | boi_RP:x24 |
| 14.2 | Guarantees to department purchases/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x67 | boi_RP:x24 |
| 15.1 | Other guarantees and liabilities/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x507 | boi_RP:x24 |
| 15.2 | Other guarantees and liabilities/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x507 | boi_RP:x24 |
| 16.1 | Unutilized credit facilities for card credits/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x74 | boi_RP:x24 |
| 16.2 | Unutilized credit facilities for card credits/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x74 | boi_RP:x24 |
| 17.1 | Unutilized revolving overdraft and other on-demand credit facilities/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x75 | boi_RP:x24 |
| 17.2 | Unutilized revolving overdraft and other on-demand credit facilities/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x75 | boi_RP:x24 |
| 18.1 | Irrevocable commitments to grant credit which has been approved but not yet drawn/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x77 | boi_RP:x24 |
| 18.2 | Irrevocable commitments to grant credit which has been approved but not yet drawn/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x77 | boi_RP:x24 |
| 19.1 | Commitments to issue guarantees/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x76 | boi_RP:x24 |
| 19.2 | Commitments to issue guarantees/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x76 | boi_RP:x24 |
| 20.1 | Total/Contract balances | boi_met:mi204 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x65 | boi_RP:x24 |
| 20.2 | Total/Allowance for credit losses | boi_met:mi3 | xbrli:monetaryItemType | instant | boi_BC:x8 | boi_CS:x1 | boi_MC:x65 | boi_RP:x24 |