| Standard label: | Subordinated Borrowings Disclosure [Text Block] |
| Name: | us-gaap:SubordinatedBorrowingsDisclosureTextBlock |
| Documentation: | The entire disclosure for borrowings under subordinated debt agreements that qualify as available in computing net capital under SEC's uniform net capital rule, including restrictive covenants, collateral, interest rates and due dates, amounts due by date and amount owed in total. |
| Object type: | cm:Level1TextBlock |
| 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:SubordinatedBorrowingsDisclosureTextBlock |
| Label | Role | Language |
| Subordinated Borrowings Disclosure [Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 942 470 45 1 | http://fasb.org/us-gaap/role/ref/legacyRef | 942 |