cm:Concept: us-gaap:GoodwillPurchaseAccountingAdjustments
| Goodwill, Purchase Accounting Adjustments |
| us-gaap:GoodwillPurchaseAccountingAdjustments |
| Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the 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) |
| Debit |
| false |
| us-gaap:GoodwillPurchaseAccountingAdjustments |