cm:Concept: us-gaap:EnvironmentalExitCostsReasonablyPossibleAdditionalLossesBestEstimate
| Environmental Exit Costs, Reasonably Possible Additional Losses, Best Estimate |
| us-gaap:EnvironmentalExitCostsReasonablyPossibleAdditionalLossesBestEstimate |
| Best estimate of the reasonably possible loss exposure in excess of the amount accrued for remediation, site restoration, postclosure, monitoring commitments, or other exit costs associated with the sale, disposal or abandonment of a particular property resulting from unanticipated contamination of the assets. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:EnvironmentalExitCostsReasonablyPossibleAdditionalLossesBestEstimate |