| Standard label: | Schedule of Assumptions for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Table Text Block] |
| Name: | us-gaap:ScheduleOfAssumptionsForFairValueAsOfBalanceSheetDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrServicingLiabilitiesTextBlock |
| Documentation: | Tabular disclosure of all information related to the key inputs and assumptions (including, at a minimum, but not limited to, and if applicable, quantitative information about discount rates, expected prepayments including the expected weighted-average life of prepayable financial assets, and anticipated credit losses) used in measuring the fair value of assets or liabilities that relate to the transferor's continuing involvement with transferred financial assets, as of the balance sheet date. |
| 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:ScheduleOfAssumptionsForFairValueAsOfBalanceSheetDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrServicingLiabilitiesTextBlock |
| Label | Role | Language |
| Schedule of Assumptions for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 860 20 50 4 (b) | http://fasb.org/us-gaap/role/ref/legacyRef | 860 |