cm:Concept: us-gaap:FiniteLivedIntangibleAssetsPurchaseAccountingAdjustments
| Finite-Lived Intangible Assets, Purchase Accounting Adjustments |
| us-gaap:FiniteLivedIntangibleAssetsPurchaseAccountingAdjustments |
| Amount of increase (decrease) to assets, excluding financial assets and goodwill, lacking physical substance with a finite life for purchase accounting adjustments. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:FiniteLivedIntangibleAssetsPurchaseAccountingAdjustments |