| Standard label: | Investment Income [Table Text Block] |
| Name: | us-gaap:InvestmentIncomeTextBlock |
| Documentation: | Tabular disclosure of investment income, including, but not limited to, interest and dividend income and amortization of discount (premium) derived from debt and equity securities. Excludes realized and unrealized gain (loss) on investments. |
| 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:InvestmentIncomeTextBlock |
| Examples of this text block disclosure: | InvestmentIncome |
| Label | Role | Language |
| Investment Income [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 220 10 S99 2 (SX 210.5-03.7(a),(b)) | http://fasb.org/us-gaap/role/ref/legacyRef | 220 |
| FASB Accounting Standards Codification 220 10 S99 2 (SX 210.5-03.8) | http://fasb.org/us-gaap/role/ref/legacyRef | 220 |
| FASB Accounting Standards Codification 220 10 S99 2 (SX 210.5-03.9) | http://fasb.org/us-gaap/role/ref/legacyRef | 220 |
| FASB Accounting Standards Codification 944 220 S99 1 (SX 210.7-04.2) | http://fasb.org/us-gaap/role/ref/legacyRef | 944 |