cm:Level3TextBlock: us-gaap:TargetedOrTrackingStockDescriptionTextBlock
| Targeted or Tracking Stock [Table Text Block] |
| us-gaap:TargetedOrTrackingStockDescriptionTextBlock |
| Tabular disclosure of quantitative and qualitative information related to target or tracking stock issued, including, but not limited to, pricing of transactions and cost allocation method used. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:TargetedOrTrackingStockDescriptionTextBlock |
| TargetedOrTrackingStock |