cm:Axis: us-gaap:MultiemployerPlanTypeAxis
| Multiemployer Plan Type [Axis] |
| us-gaap:MultiemployerPlanTypeAxis |
| Information by type of pension or 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. Types of multiemployer plans include pension benefit plans and postretirement benefit plans. |
| cm:Axis |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:MultiemployerPlanTypeAxis |