| Standard label: | Options Held [Member] |
| Name: | us-gaap:OptionMember |
| Documentation: | Contracts conveying rights, but not obligations, to buy or sell a specific commodity, or financial or equity instrument, at a specified price during a specified period (an American option) or at a specified date (a European option) which were purchased or otherwise acquired, excluding options written (for which a premium was received). |
| Object type: | cm:Member |
| Data type: | [Member] (nonnum:domainItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | true |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:OptionMember |
| Label | Role | Language |
| Options Held [Member] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 815 10 15 83 | http://fasb.org/us-gaap/role/ref/legacyRef | 815 |