cm:Level3TextBlock: us-gaap:ScheduleOfIncomeBeforeIncomeTaxDomesticAndForeignTableTextBlock
| Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] |
| us-gaap:ScheduleOfIncomeBeforeIncomeTaxDomesticAndForeignTableTextBlock |
| Tabular disclosure of income before income tax between domestic and foreign jurisdictions. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfIncomeBeforeIncomeTaxDomesticAndForeignTableTextBlock |
| IncomebeforeIncomeTaxDomesticAndForeign |