cm:Concept: us-gaap:GainLossOnComponentsExcludedFromAssessmentOfPriceRiskCashFlowHedgeEffectiveness
| Gain (Loss) on Components Excluded from Assessment of Price Risk Cash Flow Hedge Effectiveness |
| us-gaap:GainLossOnComponentsExcludedFromAssessmentOfPriceRiskCashFlowHedgeEffectiveness |
| The net gain (loss) relating to components of the gain (loss) on foreign currency cash flow hedging instruments excluded from the assessment of hedge effectiveness. Recognized in earnings. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:GainLossOnComponentsExcludedFromAssessmentOfPriceRiskCashFlowHedgeEffectiveness |