Counterparty Risk (% Of Due from Brokers) (Details) |
Jun. 30, 2018 |
|---|---|
| Morgan Stanley [Member] | |
| Concentration Risk [Line Items] | |
| % of Total Due from Brokers | 49.00% |
| J.P. Morgan Securities LLC [Member] | |
| Concentration Risk [Line Items] | |
| % of Total Due from Brokers | 17.00% |