cm:Concept: us-gaap:DescriptionOfBasisOfAccountingForTransactionsBetweenReportableSegments
| Segment Reporting, Measurement for Transactions Between Reportable Segments |
| us-gaap:DescriptionOfBasisOfAccountingForTransactionsBetweenReportableSegments |
| A description of the basis of accounting for transactions between reportable segments. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DescriptionOfBasisOfAccountingForTransactionsBetweenReportableSegments |