IndexOpen Option Contracts Written Type [Axis]
| Name | OpenOptionContractsWrittenTypeAxis |
|---|---|
| Namespace | http://fasb.org/us-gaap/2020-01-31 |
| Prefix | us-gaap |
| Data type | xbrli:stringItemType |
| Period type | duration |
| Substitution Group | xbrldt:dimensionItem |
| Balance | None |
| Nillable | True |
| Abstract | True |
Labels
| Text | Lang | Role | Container role |
|---|---|---|---|
| Open Option Contracts Written Type [Axis] | en-US | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Open Option Contracts Written Type [Axis] [No Default] | en-US | http://fasb.org/us-gaap/role/label/axisDefault | http://www.xbrl.org/2003/role/link |