cm:Concept: us-gaap:AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses
| Accrual for Environmental Loss Contingencies, Charges to Expense for New Losses |
| us-gaap:AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses |
| Amount of expense for newly incurred environmental loss contingencies. Includes, but is not limited to, remediation expense and interest accretion. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses |