cm:Concept: us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivablesCategorizedAsAvailableForSale
| Proceeds from Collection of Retained Interest in Securitized Receivables categorized as Available-for-sale |
| us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivablesCategorizedAsAvailableForSale |
| Amount of cash inflow from collection on beneficial interest in securitization of loan receivable measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivablesCategorizedAsAvailableForSale |