cm:Concept: us-gaap:NewAccountingPronouncementOrChangeInAccountingPrincipleDescriptionOfPriorperiodInformationRetrospectivelyAdjusted
| New Accounting Pronouncement or Change in Accounting Principle, Description of Prior-period Information Retrospectively Adjusted |
| us-gaap:NewAccountingPronouncementOrChangeInAccountingPrincipleDescriptionOfPriorperiodInformationRetrospectivelyAdjusted |
| Description of the prior-period information that has been retrospectively adjusted when a new accounting pronouncement or a change in accounting principle is adopted. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:NewAccountingPronouncementOrChangeInAccountingPrincipleDescriptionOfPriorperiodInformationRetrospectivelyAdjusted |