cm:Concept: us-gaap:ProceedsFromPrincipalRepaymentsOnLoansAndLeasesHeldForInvestment
| Proceeds from Principal Repayments on Loans and Leases Held-for-investment |
| us-gaap:ProceedsFromPrincipalRepaymentsOnLoansAndLeasesHeldForInvestment |
| The cash inflow from repayments of the balance excluding interest (principal) on loans receivable and leases held for investment purposes. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ProceedsFromPrincipalRepaymentsOnLoansAndLeasesHeldForInvestment |