cm:Concept: us-gaap:DescriptionOfLocationOfInterestRateFairValueHedgeDerivativeOnBalanceSheet
| Description of Location of Interest Rate Fair Value Hedge Derivative on Balance Sheet |
| us-gaap:DescriptionOfLocationOfInterestRateFairValueHedgeDerivativeOnBalanceSheet |
| Description of where the interest rate derivatives designated as fair value hedges are reported in the balance sheet. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DescriptionOfLocationOfInterestRateFairValueHedgeDerivativeOnBalanceSheet |