cm:Concept: us-gaap:DefinedBenefitPlanAssumptionsUsedInCalculationsNarrativeDescription
| Defined Benefit Plan, Assumptions Used in Calculation, Description |
| us-gaap:DefinedBenefitPlanAssumptionsUsedInCalculationsNarrativeDescription |
| Description of assumption used to determine benefit obligation and net periodic benefit cost of defined benefit plan. Includes, but is not limited to, discount rate, rate of compensation increase, expected long-term rate of return on plan assets and interest crediting rate. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DefinedBenefitPlanAssumptionsUsedInCalculationsNarrativeDescription |