cm:Concept: us-gaap:SiteContingencyRecoveryFromThirdPartyOfEnvironmentalRemediationCost
| Site Contingency, Recovery from Third Party of Environmental Remediation Cost |
| us-gaap:SiteContingencyRecoveryFromThirdPartyOfEnvironmentalRemediationCost |
| Amount of the estimated recovery from third parties recorded in the period for an individual site that reduces environmental remediation expense. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:SiteContingencyRecoveryFromThirdPartyOfEnvironmentalRemediationCost |