cm:Level3TextBlock: us-gaap:ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTextBlock
| Revenue from External Customers by Products and Services [Table Text Block] |
| us-gaap:ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTextBlock |
| Tabular disclosure of entity-wide revenues from external customers for each product or service or each group of similar products or services if the information is not provided as part of the reportable operating segment information. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTextBlock |
| RevenuefromExternalCustomersByProductsAndServices |