cm:Concept: us-gaap:DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
| Defined Benefit Plan, Plan Assets, Target Allocation, Percentage |
| us-gaap:DefinedBenefitPlanPlanAssetsTargetAllocationPercentage |
| Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. |
| cm:Concept |
| Percent (num:percentItemType) |
| As Of (instant) |
| (no balance type) |
| false |
| us-gaap:DefinedBenefitPlanPlanAssetsTargetAllocationPercentage |