cm:Level3TextBlock: us-gaap:ScheduleOfUnrecognizedCompensationCostNonvestedAwardsTableTextBlock
| Share-based Payment Arrangement, Nonvested Award, Cost [Table Text Block] |
| us-gaap:ScheduleOfUnrecognizedCompensationCostNonvestedAwardsTableTextBlock |
| Tabular disclosure of cost not yet recognized and weighted-average period over which cost is expected to be recognized for nonvested award under share-based payment arrangement. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfUnrecognizedCompensationCostNonvestedAwardsTableTextBlock |
| UnrecognizedCompensationCostNonvestedAwards |