| Standard label: | DJIA Index Future [Member] |
| Name: | us-gaap:DJIAIndexFutureMember |
| Documentation: | A standardized contract, traded on a futures exchange, to buy or sell Dow Jones Industrial Average (DJIA) Index at a certain date in the future, at a certain price. |
| 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:DJIAIndexFutureMember |
| Label | Role | Language |
| DJIA Index Future [Member] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |