| Standard label: | Defined Benefit Plan, Plan Assets, Allocation [Table Text Block] |
| Name: | us-gaap:DefinedBenefitPlanPlanAssetsAllocationTableTextBlock |
| Documentation: | Tabular disclosure of investment allocation of defined benefit plan assets. Includes, but is not limited to, investment allocation percentage or range of percentages. |
| Object type: | cm:Level3TextBlock |
| Data type: | Text Block (HTML) (nonnum:textBlockItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:DefinedBenefitPlanPlanAssetsAllocationTableTextBlock |
| Label | Role | Language |
| Defined Benefit Plan, Plan Assets, Allocation [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 715 20 50 1 (d)(i) | http://www.xbrl.org/2009/role/commonPracticeRef | 715 |