cm:Level2TextBlock: us-gaap:LoansAndLeasesReceivablePrepaymentEstimateAssumptionsPolicy
| Loans and Leases Receivable, Prepayment Estimate Assumptions, Policy [Policy Text Block] |
| us-gaap:LoansAndLeasesReceivablePrepaymentEstimateAssumptionsPolicy |
| Disclosure of accounting policy for the anticipation of prepayments and significant assumptions underlying prepayment estimates for amortization of premiums, discounts, and nonrefundable fees and costs if the entity holds a large number of similar loans and anticipates prepayments. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:LoansAndLeasesReceivablePrepaymentEstimateAssumptionsPolicy |