cm:Concept: us-gaap:ProceedsFromSaleOfSecuritiesOperatingActivities
| Proceeds from Sale of Securities, Operating Activities |
| us-gaap:ProceedsFromSaleOfSecuritiesOperatingActivities |
| Cash received from sale of investments in debt and equity securities, classified as operating activities, during the period; includes trading securities and any other investments classified as operating. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ProceedsFromSaleOfSecuritiesOperatingActivities |