cm:Concept: us-gaap:ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod
| Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method |
| us-gaap:ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod |
| Amount of interest income on financing receivables, for which there is a related allowance for credit losses, recognized on a cash-basis method of accounting that the financing receivables were impaired. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod |