cm:Concept: us-gaap:CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesAccretableYieldAdditions
| Certain Loans Acquired in Transfer Accounted for as Debt Securities, Accretable Yield, Additions |
| us-gaap:CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesAccretableYieldAdditions |
| Increases in the aggregate excess of a loan's cash flows expected to be collected over the investor's initial investment in the loan due to the acquisition of similar loans accounted for as debt securities during the period. This relates to loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesAccretableYieldAdditions |