cm:Level3TextBlock: us-gaap:BusinessAcquisitionProFormaInformationTextBlock
| Business Acquisition, Pro Forma Information [Table Text Block] |
| us-gaap:BusinessAcquisitionProFormaInformationTextBlock |
| Tabular disclosure of pro forma results of operations for a material business acquisition or series of individually immaterial business acquisitions that are material in the aggregate. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:BusinessAcquisitionProFormaInformationTextBlock |
| BusinessAcquisitionProFormaInformation |