| Standard label: | Credit Loss, Financial Instrument [Text Block] |
| Name: | us-gaap:CreditLossFinancialInstrumentTextBlock |
| Documentation: | The entire disclosure for credit loss on financial instrument measured at amortized cost basis, net investment in lease, off-balance sheet credit exposure, and available-for-sale debt security. |
| 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:CreditLossFinancialInstrumentTextBlock |
| Label | Role | Language |
| Credit Loss, Financial Instrument [Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 326 20 50 5 | http://www.xbrl.org/2003/role/disclosureRef | 326 |
| FASB Accounting Standards Codification 326 20 50 8 | http://www.xbrl.org/2003/role/disclosureRef | 326 |
| FASB Accounting Standards Codification 326 20 50 11 | http://www.xbrl.org/2003/role/disclosureRef | 326 |
| FASB Accounting Standards Codification 326 20 50 20 | http://www.xbrl.org/2003/role/disclosureRef | 326 |
| FASB Accounting Standards Codification 326 20 50 21 | http://www.xbrl.org/2003/role/disclosureRef | 326 |
| FASB Accounting Standards Codification 326 30 50 4 | http://www.xbrl.org/2003/role/disclosureRef | 326 |
| FASB Accounting Standards Codification 326 30 50 7 | http://www.xbrl.org/2003/role/disclosureRef | 326 |