cm:Concept: us-gaap:ConcentrationRiskLaborSubjectToCollectiveBargainingArrangements
| Concentration Risk, Labor Subject to Collective Bargaining Arrangements |
| us-gaap:ConcentrationRiskLaborSubjectToCollectiveBargainingArrangements |
| Description of any concentration of labor subject to collective bargaining agreements, including the general nature of the risk. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ConcentrationRiskLaborSubjectToCollectiveBargainingArrangements |