cm:Level3TextBlock: us-gaap:DefinedContributionPlanDisclosuresTableTextBlock
| Defined Contribution Plan Disclosures [Table Text Block] |
| us-gaap:DefinedContributionPlanDisclosuresTableTextBlock |
| Tabular disclosure of defined contribution pension plans or defined contribution other postretirement plans, separately for pension plans and other postretirement benefit plans. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DefinedContributionPlanDisclosuresTableTextBlock |