| Standard label: | Debt Securities, Held-to-maturity, Allowance for Credit Loss [Table Text Block] |
| Name: | us-gaap:DebtSecuritiesHeldToMaturityAllowanceForCreditLossTableTextBlock |
| Documentation: | Tabular disclosure of allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity). |
| 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:DebtSecuritiesHeldToMaturityAllowanceForCreditLossTableTextBlock |
| Label | Role | Language |
| Debt Securities, Held-to-maturity, Allowance for Credit Loss [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 326 20 50 13 | http://www.xbrl.org/2009/role/commonPracticeRef | 326 |