cm:Member: us-gaap:MultiemployerPlansPostretirementBenefitMember
| Multiemployer Plans, Postretirement Benefit [Member] |
| us-gaap:MultiemployerPlansPostretirementBenefitMember |
| Postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:MultiemployerPlansPostretirementBenefitMember |