cm:Level3TextBlock: us-gaap:ScheduleOfBenefitObligationsInExcessOfFairValueOfPlanAssetsTableTextBlock
| Defined Benefit Plan, Plan with Projected Benefit Obligation in Excess of Plan Assets [Table Text Block] |
| us-gaap:ScheduleOfBenefitObligationsInExcessOfFairValueOfPlanAssetsTableTextBlock |
| Tabular disclosure of benefit obligation and plan assets for defined benefit pension plan with projected benefit obligation in excess of plan assets. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
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| us-gaap:ScheduleOfBenefitObligationsInExcessOfFairValueOfPlanAssetsTableTextBlock |
| BenefitObligationsInExcessOfFairValueOfPlanAssets |