cm:Concept: us-gaap:CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesAcquiredDuringPeriodNotAccountedForUsingIncomeRecognitionModelAtAcquisitionAtCarryingValue
| Certain Loans Acquired in Transfer Accounted for as Debt Securities, Acquired During Period, Not Accounted for Using Income Recognition Model, at Acquisition, at Carrying Value |
| us-gaap:CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesAcquiredDuringPeriodNotAccountedForUsingIncomeRecognitionModelAtAcquisitionAtCarryingValue |
| The recorded value, at the acquisition date, of loans for which the income recognition model was not applied. This relates to loans accounted for as debt securities acquired during the period, 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) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesAcquiredDuringPeriodNotAccountedForUsingIncomeRecognitionModelAtAcquisitionAtCarryingValue |