| Standard label: | Realized Gain (Loss) on Investments [Table Text Block] |
| Name: | us-gaap:RealizedGainLossOnInvestmentsTableTextBlock |
| Documentation: | Tabular disclosure of realized gains and losses on investments reported in the statement of income. |
| 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:RealizedGainLossOnInvestmentsTableTextBlock |
| Examples of this text block disclosure: | RealizedGainLossonInvestments |
| Label | Role | Language |
| Realized Gain (Loss) on Investments [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |