cm:Concept: us-gaap:MultiemployerPlansBusinessCombinationOrDivestitureDescription
| Multiemployer Plans, Business Combination or Divestiture, Description |
| us-gaap:MultiemployerPlansBusinessCombinationOrDivestitureDescription |
| Description of the nature and effect of a business combination or divestiture on a 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. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:MultiemployerPlansBusinessCombinationOrDivestitureDescription |