cm:Concept: us-gaap:DefinedBenefitPlanNetPeriodicBenefitCostCreditExcludingServiceCostStatementOfIncomeOrComprehensiveIncomeExtensibleList
| Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible List] |
| us-gaap:DefinedBenefitPlanNetPeriodicBenefitCostCreditExcludingServiceCostStatementOfIncomeOrComprehensiveIncomeExtensibleList |
| Indicates line item in statement of income or comprehensive income that includes components of net periodic benefit cost (credit), excluding service cost component, for defined benefit plan. |
| cm:Concept |
| srt-types:extensibleListItemType |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DefinedBenefitPlanNetPeriodicBenefitCostCreditExcludingServiceCostStatementOfIncomeOrComprehensiveIncomeExtensibleList |