cm:Level3TextBlock: us-gaap:ScheduleOfAccumulatedAndProjectedBenefitObligationsTableTextBlock
| Schedule of Accumulated and Projected Benefit Obligations [Table Text Block] |
| us-gaap:ScheduleOfAccumulatedAndProjectedBenefitObligationsTableTextBlock |
| Tabular disclosure of benefit obligations including accumulated benefit obligation and projected benefit obligation. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfAccumulatedAndProjectedBenefitObligationsTableTextBlock |
| AccumulatedAndProjectedBenefitObligations |