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