cm:Concept: us-gaap:GainFromComponentsExcludedFromAssessmentOfFairValueHedgeEffectiveness
| Gain from Components Excluded from Assessment of Fair Value Hedge Effectiveness |
| us-gaap:GainFromComponentsExcludedFromAssessmentOfFairValueHedgeEffectiveness |
| Gain 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) |
| Credit |
| false |
| us-gaap:GainFromComponentsExcludedFromAssessmentOfFairValueHedgeEffectiveness |