cm:Concept: us-gaap:InterestExpenseOnForeignDepositLiabilitiesDescription
| Interest Expense on Foreign Deposit Liabilities, Description |
| us-gaap:InterestExpenseOnForeignDepositLiabilitiesDescription |
| Description of interest expense on deposit liabilities in foreign banking offices. This disclosure may include methodology, assumptions and interest expense for various types of foreign deposit liabilities. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:InterestExpenseOnForeignDepositLiabilitiesDescription |