cm:Concept: us-gaap:SiteContingencyIndicationAccrualMayChange
| Site Contingency, Indication Accrual May Change |
| us-gaap:SiteContingencyIndicationAccrualMayChange |
| Disclosure that it is reasonably possible that a change in an estimate of the obligation will occur in the near term when information available prior to issuance of the financial statements indicates that it is at least reasonably possible that the site accrual estimate will change due to one or more future confirming events. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:SiteContingencyIndicationAccrualMayChange |