cm:Concept: us-gaap:LossFromComponentsExcludedFromAssessmentOfFairValueHedgeEffectiveness
| Loss from Components Excluded from Assessment of Fair Value Hedge Effectiveness |
| us-gaap:LossFromComponentsExcludedFromAssessmentOfFairValueHedgeEffectiveness |
| Loss relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:LossFromComponentsExcludedFromAssessmentOfFairValueHedgeEffectiveness |