cm:Concept: us-gaap:DefinedBenefitPlanSignificantTransactionsBetweenEmployerOrRelatedPartiesAndPlanDuringYear
| Defined Benefit Plan, Related Party Transaction, Description |
| us-gaap:DefinedBenefitPlanSignificantTransactionsBetweenEmployerOrRelatedPartiesAndPlanDuringYear |
| Description of transaction between employer, or its related parties, and defined benefit plan. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DefinedBenefitPlanSignificantTransactionsBetweenEmployerOrRelatedPartiesAndPlanDuringYear |