cm:Concept: us-gaap:LineItemForGainLossOnPriceRiskFairValueHedgeDerivativeInFinancialStatements
| Line Item for Gain (Loss) on Price Risk Fair Value Hedge Derivative in Financial Statements |
| us-gaap:LineItemForGainLossOnPriceRiskFairValueHedgeDerivativeInFinancialStatements |
| Line item caption in which the net gain (loss) on price risk 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:LineItemForGainLossOnPriceRiskFairValueHedgeDerivativeInFinancialStatements |