cm:Concept: us-gaap:DescriptionOfLocationOfGainLossOnInterestRateFairValueHedgeDerivativeInFinancialStatements
| Description of Location of Gain (Loss) on Interest Rate Fair Value Hedge Derivative in Financial Statements |
| us-gaap:DescriptionOfLocationOfGainLossOnInterestRateFairValueHedgeDerivativeInFinancialStatements |
| Description of where the net gain (loss) on interest rate derivatives designated as fair value hedges are reported in the statement of income or other statement of financial performance. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DescriptionOfLocationOfGainLossOnInterestRateFairValueHedgeDerivativeInFinancialStatements |