cm:Concept: us-gaap:AccrualForEnvironmentalLossContingenciesSignificantAssumptions
| Accrual for Environmental Loss Contingencies, Significant Assumptions |
| us-gaap:AccrualForEnvironmentalLossContingenciesSignificantAssumptions |
| Significant assumptions underlying the estimate of the environmental loss contingencies accrual, which represents costs to remediate environmental problems. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:AccrualForEnvironmentalLossContingenciesSignificantAssumptions |