| Standard label: | Summary of Income Tax Contingencies [Table Text Block] |
| Name: | us-gaap:SummaryOfIncomeTaxContingenciesTextBlock |
| Documentation: | Tabular disclosure for tax positions taken in the tax returns filed or to be filed for which it is more likely than not that the tax position will not be sustained upon examination by taxing authorities and other income tax contingencies. Includes, but is not limited to, interest and penalties, reconciliation of unrecognized tax benefits, unrecognized tax benefits that would affect the effective tax rate, tax years that remain subject to examination by tax jurisdictions, and information about positions for which it is reasonably possible that amounts unrecognized will significantly change within 12 months. |
| 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:SummaryOfIncomeTaxContingenciesTextBlock |
| Examples of this text block disclosure: | IncomeTaxContingency |
| Label | Role | Language |
| Summary of Income Tax Contingencies [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 740 10 50 15A | http://fasb.org/us-gaap/role/ref/legacyRef | 740 |
| FASB Accounting Standards Codification 740 10 50 15 (d) | http://fasb.org/us-gaap/role/ref/legacyRef | 740 |
| FASB Accounting Standards Codification 740 10 50 19 | http://fasb.org/us-gaap/role/ref/legacyRef | 740 |