cm:Concept: us-gaap:GoodwillWrittenOffRelatedToSaleOfBusinessUnit
| Goodwill, Written off Related to Sale of Business Unit |
| us-gaap:GoodwillWrittenOffRelatedToSaleOfBusinessUnit |
| Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:GoodwillWrittenOffRelatedToSaleOfBusinessUnit |