cm:Concept: us-gaap:EnvironmentalExitCostsImpairmentAssessment
| Environmental Exit Costs, Impairment Assessment |
| us-gaap:EnvironmentalExitCostsImpairmentAssessment |
| Describes how the necessary expenditures are considered in the assessment of the asset's value and the possible need to reflect an impairment loss if an asset held for sale or development will require remediation to be performed before development, sale, or as a condition of sale. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:EnvironmentalExitCostsImpairmentAssessment |