| Standard label: | Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] |
| Name: | us-gaap:ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock |
| Documentation: | Tabular disclosure of assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). |
| 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:ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock |
| Label | Role | Language |
| Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 820 10 50 2 (a) | http://www.xbrl.org/2003/role/disclosureRef | 820 |
| FASB Accounting Standards Codification 820 10 50 2 (b) | http://www.xbrl.org/2003/role/disclosureRef | 820 |