cm:Level3TextBlock: us-gaap:NewAccountingPronouncementEarlyAdoptionTableTextBlock
| New Accounting Pronouncement, Early Adoption [Table Text Block] |
| us-gaap:NewAccountingPronouncementEarlyAdoptionTableTextBlock |
| Tabular disclosure of financial statement line items and the effect of the guidance on the financial statement line items if the entity elects early adoption of accounting guidance. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:NewAccountingPronouncementEarlyAdoptionTableTextBlock |
| NewAccountingPronouncementEarlyAdoption |