cm:Concept: us-gaap:IndefiniteLivedIntangibleAssetsWrittenOffRelatedToSaleOfBusinessUnit
| Indefinite-lived Intangible Assets, Written off Related to Sale of Business Unit |
| us-gaap:IndefiniteLivedIntangibleAssetsWrittenOffRelatedToSaleOfBusinessUnit |
| Amount of divestiture of an asset lacking physical substance and having a projected indefinite period of benefit to fair value. Excludes financial assets and goodwill. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:IndefiniteLivedIntangibleAssetsWrittenOffRelatedToSaleOfBusinessUnit |