cm:Concept: us-gaap:AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesExpectedCreditLosses
| Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Expected Credit Losses |
| us-gaap:AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesExpectedCreditLosses |
| Rate at which principal will not be repaid on securitized financial assets regardless of when the transfer occurred. |
| cm:Concept |
| Percent (num:percentItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesExpectedCreditLosses |