cm:Concept: us-gaap:SiteContingencyLossExposureInExcessOfAccrualDescription
| Site Contingency, Loss Exposure in Excess of Accrual, Description |
| us-gaap:SiteContingencyLossExposureInExcessOfAccrualDescription |
| Nature of the reasonably possible loss contingency and estimate of the reasonably possible loss exposure in excess of the amount accrued for environmental loss contingencies at an individual site. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:SiteContingencyLossExposureInExcessOfAccrualDescription |