| Standard label: | Schedule of Price Risk Derivatives [Table Text Block] |
| Name: | us-gaap:ScheduleOfPriceRiskDerivativesTableTextBlock |
| Documentation: | Tabular disclosure of price risk derivatives, including, but not limited to, the fair value of the derivatives, statement of financial position location, and statement of financial performance location of these instruments. |
| 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:ScheduleOfPriceRiskDerivativesTableTextBlock |
| Label | Role | Language |
| Schedule of Price Risk Derivatives [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 815 10 50 4C | http://fasb.org/us-gaap/role/ref/legacyRef | 815 |