cm:Concept: us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear
| Accrual for Environmental Loss Contingencies, Undiscounted, Next Twelve Months |
| us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear |
| Undiscounted amount of the accrual for environmental loss contingencies expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear |