cm:Concept: us-gaap:IndefiniteLivedIntangibleAssetsPurchaseAccountingAdjustments
| Indefinite-lived Intangible Assets, Purchase Accounting Adjustments |
| us-gaap:IndefiniteLivedIntangibleAssetsPurchaseAccountingAdjustments |
| Amount of increase (decrease) of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit, from purchase accounting adjustments. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:IndefiniteLivedIntangibleAssetsPurchaseAccountingAdjustments |