cm:Level3TextBlock: us-gaap:ScheduleOfEffectOfSignificantUnobservableInputsChangesInPlanAssetsTableTextBlock
| Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block] |
| us-gaap:ScheduleOfEffectOfSignificantUnobservableInputsChangesInPlanAssetsTableTextBlock |
| Tabular disclosure of the effect of fair value measurements using significant unobservable inputs (Level 3) on changes in plan assets of pension plans and/or other employee benefit plans for the period. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfEffectOfSignificantUnobservableInputsChangesInPlanAssetsTableTextBlock |
| EffectOfSignificantUnobservableInputsChangesInPlanAssets |