| Standard label: | Schedule of Servicing Assets at Fair Value [Table Text Block] |
| Name: | us-gaap:ScheduleOfServicingAssetsAtFairValueTextBlock |
| Documentation: | Tabular disclosure of the activity in the balance of servicing assets (including a description of where changes in fair value are reported in the statement of income for each period for which results of operations are presented), including but not limited to, the following: beginning and ending balances, additions (for instance, through purchases of servicing assets), disposals, changes in fair value during the period resulting from changes in inputs or assumptions used in the valuation model, other changes in fair value along with a description of those changes, and other changes that affect the balance along with a description of those changes. |
| 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:ScheduleOfServicingAssetsAtFairValueTextBlock |
| Label | Role | Language |
| Schedule of Servicing Assets at Fair Value [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 860 50 50 3 (a) | http://fasb.org/us-gaap/role/ref/legacyRef | 860 |