cm:Concept: us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivablesCategorizedAsHeldToMaturity
| Proceeds from Collection of Retained Interest in Securitized Receivables categorized as Held-to-maturity |
| us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivablesCategorizedAsHeldToMaturity |
| Amount of cash inflow from collection on beneficial interest in securitization of loan receivable measured at amortized cost. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivablesCategorizedAsHeldToMaturity |