cm:Concept: us-gaap:GainLossOnComponentsExcludedFromAssessmentOfPriceRiskHedgeEffectiveness
| Gain (Loss) on Components Excluded from Assessment of Price Risk Hedge Effectiveness |
| us-gaap:GainLossOnComponentsExcludedFromAssessmentOfPriceRiskHedgeEffectiveness |
| The net gain (loss) recognized in earnings in the period relating to components of the gain (loss) on price risk hedging instruments excluded from the assessment of hedge effectiveness. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:GainLossOnComponentsExcludedFromAssessmentOfPriceRiskHedgeEffectiveness |