cm:Concept: us-gaap:IncreaseDecreaseInPensionAndPostretirementObligations
| Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits |
| us-gaap:IncreaseDecreaseInPensionAndPostretirementObligations |
| Amount of increase (decrease) in obligation for pension and other postretirement benefits. Includes, but is not limited to, defined benefit and defined contribution plans. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:IncreaseDecreaseInPensionAndPostretirementObligations |