cm:Level3TextBlock: us-gaap:InterimPeriodCostsNotAllocableTableTextBlock
| Interim Period, Costs Not Allocable [Table Text Block] |
| us-gaap:InterimPeriodCostsNotAllocableTableTextBlock |
| Tabular disclosure of costs and expenses incurred during an interim period that cannot be readily identified with the activities or benefits of other interim periods and are charged to the interim period in which incurred. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:InterimPeriodCostsNotAllocableTableTextBlock |