cm:Level2TextBlock: us-gaap:LoansAndLeasesReceivableNonmortgageLoanValuationPolicy
| Nonmortgage Loan, Valuation [Policy Text Block] |
| us-gaap:LoansAndLeasesReceivableNonmortgageLoanValuationPolicy |
| Disclosure of accounting policy for determining the lower of cost or market value of loans that are unsecured or secured by collateral other than real property, and whether the method is applied to an individual loan or to an aggregate portfolio of loans. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:LoansAndLeasesReceivableNonmortgageLoanValuationPolicy |