cm:Concept: us-gaap:OtherIncreaseDecreaseInEnvironmentalLiabilities
| Other Increase (Decrease) in Environmental Liabilities |
| us-gaap:OtherIncreaseDecreaseInEnvironmentalLiabilities |
| Other increase (decrease) not attributable to current expense nor cash payments during an accounting period in estimated obligations recorded for probable future costs attributable to environmental contamination issues. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:OtherIncreaseDecreaseInEnvironmentalLiabilities |