cm:Concept: us-gaap:DefinedBenefitPlanDescriptionOfAnySubstantiveCommitmentUsedAsBasisForAccountingForBenefitObligation
| Defined Benefit Plan, Substantive Commitment Used as Basis for Accounting for Benefit Obligation, Description |
| us-gaap:DefinedBenefitPlanDescriptionOfAnySubstantiveCommitmentUsedAsBasisForAccountingForBenefitObligation |
| Description of substantive commitment used as basis for accounting for benefit obligation of defined benefit plan. Includes, but is not limited to, past practice or history of regular benefit increases. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DefinedBenefitPlanDescriptionOfAnySubstantiveCommitmentUsedAsBasisForAccountingForBenefitObligation |