cm:Level2TextBlock: us-gaap:ShareBasedCompensationForfeituresPolicyTextBlock
| Share-based Payment Arrangement, Forfeiture [Policy Text Block] |
| us-gaap:ShareBasedCompensationForfeituresPolicyTextBlock |
| Disclosure of accounting policy election for determining cost for share-based payment arrangement by either estimating forfeiture expected to occur or by recognizing effect of forfeiture upon occurrence. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ShareBasedCompensationForfeituresPolicyTextBlock |