| Name | UnderwritingIncomeLoss |
|---|---|
| Namespace | http://fasb.org/us-gaap/2020-01-31 |
| Prefix | us-gaap |
| Data type | xbrli:monetaryItemType |
| Period type | duration |
| Substitution Group | xbrli:item |
| Balance | credit |
| Nillable | True |
| Abstract | False |
| Text | Lang | Role | Container role |
|---|---|---|---|
| The difference between the price paid by the public and the contract price less the related expenses. A broker-dealer may underwrite a security offering by contracting to buy the issue either at a fixed price or a price based on selling the offering on a best-effort basis. | en-US | http://www.xbrl.org/2003/role/documentation | http://www.xbrl.org/2003/role/link |
| Underwriting Income (Loss) | en-US | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |