| Standard label: | Open Option Contracts Written, Expiration Date |
| Name: | us-gaap:OpenOptionContractsWrittenExpirationDates |
| Documentation: | Expiration date of the open option contracts written on the investment, in CCYY-MM-DD format. |
| Object type: | cm:Concept |
| Data type: | Date (xbrli:dateItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:OpenOptionContractsWrittenExpirationDates |
| Label | Role | Language |
| Open Option Contracts Written, Expiration Date | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 946 320 S99 3 (SX 210.12-12B.Column D) | http://fasb.org/us-gaap/role/ref/legacyRef | 946 |